Case4: 47 year old male

DiseaseAssertion: Carried the MYBPC3 R326Q mutation

FamilyInfo:His father had onset of symptoms at 77 years of age and is stable on medication. Two asymptomatic young children (M21, III:1 and :2) had no signs of hypertrophy or dilatation on echocardiography and normal ECG.

ParentalTesting: NR

CasePresentingHPOs: HP:0011713, HP:0034307, HP:0012665, HP:0001635

CaseHPOFreeText: Had onset of symptoms at 42 years, LBBB on ECG and required cardiac resynchronization therapy. Has left ventricular end diastolic diameter (in mm and indexed by body surface area (cm/m2) of 81 mm and 3.6 cm/m2. A left ventricular ejection fraction as 20%. ECG as left bundle branch block. Clinical status as DCM/ congestive heart failure. CAG as normal. As well with cardiac resynchronization therapy.

CaseNotHPOs: HP:0011675

CaseNotHPOFreeText: No arrhythmia

CasePreviousTesting:NR

Genotyping Method:Genetically screened, also using GenBank with PCR by amplifying the coding region

FunctionalAnalysis: It results in the replacement of a conserved charged arginine with neutral glutamine at residue 326 in the phosphorylatable MyBPC motif of cMyBPC. This charge change is likely to cause functional impairment.

Variant:NM_000256.3:c.977G>A

ClinVar:42813

CAID:CA016212

gnomAD: gnomAD v2: 11:47367871 C / T gnomAD v3: 11:47346320 C / T gnomAD v4: chr11-47346320-C-T

AdditionalInfo:NR

Case5: 65 year-old male

DiseaseAssertion: carried a known TNNT2 K247R mutation as well as two novel intronic variants in MYH7 (IVS39+7C>A) and MYBPC3 (IVS25+13T>A)

FamilyInfo: None of his five siblings were affected, judged by their clinical presentation, nor was there any history of cardiac disease or sudden death in the family.

ParentalTesting:NR

CasePresentingHPOs:HP:0003677, HP:0012828, HP:0001635, HP:0005110, HP:0034307, HP:0012666,

CaseHPOFreeText: had late-onset at age 47 IDC, with a slow progression to severe heart failure and subsequently HTX. He also suffered from atrial fibrillation in the later stages of his disease. Had left ventricular end diastolic diameter (in mm and indexed by body surface area (cm/m2)) with a value of 68mm and 3.4cm/m2. As well with 30% of left ventricular ejection fraction. His ECG is normal, clinical status is heart transplantation from the age of 56. CAG is normal.

CaseNotHPOs:NR

CaseNotHPOFreeText:NR

CasePreviousTesting:NR

Genotyping Method:Genetically screened, also using GenBank with PCR by amplifying the coding region

FunctionalAnalysis: The variant could thus possibly result in the synthesis of a limited amount of the slightly modified β-myosin. The functional significance of this is not easily established, but it suggests that the variant may be a disease modifier.

Variant:NM_001276345.2:c.869A>G

ClinVar:4881578

CAID:CA344201883

gnomAD:NR

AdditionalInfo: MYH7 (IVS39+7C>A) increased the likelihood of a cryptic donor splice site to 70%, possibly resulting in the synthesis of mRNA coding for a β-myosin with a C terminus of –VGLE instead of –GLNEE. As the variant is located in the last exon, the faulty spliced mRNA is probably not degraded but results in the synthesis of a modified protein.

Case 7: 47 year old male

DiseaseAssertion: novel MYH7 R1832C in the index case

FamilyInfo:His father died at the age of 47 years due to IDC, whereas a sibling of the index case died suddenly within her first year. It was not possible to obtain DNA from the deceased relatives.

ParentalTesting:NR

CasePresentingHPOs:HP:0012828,HP:0012835, HP:0034307, HP:0012666

CaseHPOFreeText: He had an early onset of symptoms, in his third decade as being the age of 33, with severe dilatation of his left ventricle and depressed LVEF, and required HTX 3 years after the onset of symptoms. A left ventricular end diastolic diameter (in mm and indexed by body surface area (cm/m2)); value of 86mm and 3.2cm/m2. Has a left ventricular ejection fraction of 20%. His clinical status is heart transplantation.

CaseNotHPOs:NR

CaseNotHPOFreeText:NR

CasePreviousTesting:NR

Genotyping Method:NR

FunctionalAnalysis:NR

Variant:NM_000257.4:c.5494C>T

ClinVar:161322

CAID:CA016134

gnomAD: gnomAD v2: 14:23884269 G / A gnomAD v3: 14:23415060 G / A gnomAD v4: chr14-23415060-G-A

AdditionalInfo: This mutation is located in the rod portion of MYH7 and replaces a basic arginine residue with a reactive neutral cysteine residue in the g-position of the heptad repeat in the α-helical myosin rod, and thus may destabilize the salt bridges required for myosin–myosin dimerization.

Case8: 56 year old male

DiseaseAssertion: A double heterozygous for the known MYBPC3 R326Q mutation.

FamilyInfo: His father died due to IDC in his fourth decade, whereas his brother developed IDC. DNA was not available from either of these individuals.

ParentalTesting:NR

CasePresentingHPOs:HP:0005110, HP:0034307,HP:0012666, HP:0011675, HP:0005110, HP:0100651

CaseHPOFreeText: He also developed atrial fibrillation, well regulated on medication. Had onset conditions at age 36. He had left ventricular end diastolic diameter (in mm and indexed by body surface area (cm/m2)); as a value of 65mm and 3.2 cm/m2. A LVEF, left ventricular ejection fraction as 15%. Arrhythmia level as atrial fibrillation. Clinical status as heart transplantation. He also has type 1 diabetes mellitus

CaseNotHPOs:NR

CaseNotHPOFreeText:NR

CasePreviousTesting:NR

Genotyping Method:NR

FunctionalAnalysis:NR

Variant:NM_000256.3:c.977G>A

ClinVar:42813

CAID:CA016212

gnomAD:gnomAD v2: 11:47367871 C / T gnomAD v3: 11:47346320 C / T gnomAD v4: chr11-47346320-C-T

AdditionalInfo:NR

Case1: A 68-year-old female

DiseaseAssertion: dilated cardiomyopathy (DCM), with the MYH7 p.Lys637Glu (K637E) variant identified in the affected patient. The study investigated sarcomeric gene variants associated with DCM

FamilyInfo: The proband's father (M1, II:3) died suddenly at 36 years of age, 2 years after being diagnosed with DCM.

ParentalTesting: Yes from father

CasePresentingHPOs: HP:0011664, HP:0011713, HP:0003677, HP:0001635,

CaseHPOFreeText: was diagnosed as having left ventricular non-compaction (LVNC) based on echocardiography. A left bundle branch block on her ECG. Echocardiography revealed LVNC and she has had a slow progression towards heart failure and an increasing dilatation of her left ventricle. Age 48 at onset, left ventricular end diastolic diameter 59 mm, left ventricular ejection fraction 25%, ventricular extrasystoles for arrhythmia.

CaseNotHPOs:NR

CaseNotHPOFreeText:NR

CasePreviousTesting:NR

Genotyping Method: genetically screened, also using GenBank with PCR by amplifying the coding region

FunctionalAnalysis:NR

Variant: NM_000257.4:c.1909A>G

ClinVar: 1329402

CAID:CA389049558

gnomAD: NR

AdditionalInfo: NR

Case 3: A 64 year old female

DiseaseAssertion: The case carried the novel MYH7 K637E mutation

FamilyInfo: Her mother died of a suspected but unconfirmed cardiac cause; thus, this was regarded as a non-FDC case. Two healthy sisters declined participation in the study.

ParentalTesting:NR

CasePresentingHPOs: HP:0003674, HP:0034307, HP:0002372, HP:0011675, HP:0005110

CaseHPOFreeText: Slowly from onset of symptoms at the age of 42 years, and received HTX in her sixth decade. Has left ventricular end diastolic diameter (in mm and indexed by body surface area (cm/m2)), 81mm and then 4.2m2. LVEF as 15%, ECG as normal. Arrhythmia as atrial fibrillation. NYHA as 4. Clinical status as heart transplantation. CAG has a normal level.

CaseNotHPOs:NR

CaseNotHPOFreeText:NR

CasePreviousTesting:NR

Genotyping Method: Genetically screened, also using GenBank with PCR by amplifying the coding region

FunctionalAnalysis: NR

Variant:NM_000257.4:c.1909A>G

ClinVar:1329402

CAID:CA389049558

gnomAD:NR

AdditionalInfo:NR

Case6: 48 year old male

DiseaseAssertion: Carried the MYBPC3 E619K mutation

FamilyInfo:Three unaffected children were examined (IV:1, IV:2 and IV:3), all with normal echocardiography without signs of hypertrophy or dilatation. Both affected individuals as well as a 26-year-old unaffected daughter (M29, IV:3) carried the MYBPC3 E619K mutation

ParentalTesting:NR

CasePresentingHPOs: HP:0034307, HP:0012666, HP:0011713, HP:0001635

CaseHPOFreeText: Onset of symptoms in their third decade; the index case required heart transplantation 3 years after the onset of symptoms. Has onset at the age of 37. Has left ventricular end diastolic diameter (in mm and indexed by body surface area (cm/m2)) with the value of 79 mm and 3.2 cm/m2. They have a 20% of left ventricular ejection fraction. ECG as left bundle branch block. Clinical status as DCM/ congestive heart failure. CAG as normal.

CaseNotHPOs:NR

CaseNotHPOFreeText:NR

CasePreviousTesting:NR

Genotyping Method:Genetically screened, also using GenBank with PCR by amplifying the coding region

FunctionalAnalysis:NR

Variant: NM_000256.3:c.1855G>A

ClinVar:161303

CAID:CA011336

gnomAD: gnomAD v2: 11:47362731 C / T gnomAD v3: 11:47341180 C / T gnomAD v4: chr11-47341180-C-T

AdditionalInfo:NR

PMID: 41561115

Gene: MYBPC3

HGNC ID: 7551

Case1: 40-year-old Chinese male

DiseaseAssertion: exertional dyspnea for one year and substernal chest pain for one week.

FamilyInfo: Father experienced sudden cardiac death (SCD) at the age of 41. Targeted region capture and second-generation high throughput sequencing were performed on the proband’s cousin, cousin sister, and sister. Results demonstrated that all family members carried the MYBPC3 c.1827dupC variant. Pedigree in Fig. 3

ParentalTesting: NR

CasePresentingHPOs: HP:0025169, HP:0025168, HP:0031675, HP:0001714,

CaseHPOFreeText: harsh systolic ejection murmur at the left sternal border (3rd–4th intercostal spaces), accentuated by Valsalva maneuver. Echocardiography revealed the following key findings: severe asymmetric septal hypertrophy, characterized by an interventricular septal thickness (IVsd) at end-diastole of 25–30 mm and a left ventricular posterior wall dimensions (LVPWd) of 21 mm, with a preserved left ventricular ejection fraction (LVEF) of 59%

CaseNotHPOs: NR

CaseNotHPOFreeText: NR

CasePreviousTesting: target-region capture sequencing and second-generation high throughput sequencing were performed to analyze all exons and their Flanking regions. Rare and known variants were validated using Sanger sequencing and cascade screening was carried out for all available relatives

Genotyping Method: target-region capture sequencing and second-generation high throughput sequencing, Sanger sequencing and cascade screening.

FunctionalAnalysis:NR

Variant: NM_000256.3:c.1827dupC, NM_004415.4:c.1324T>C

ClinVar:NR

CAID:UnregisteredVariant

gnomAD:NR

Case2: 16-year-old male patient

DiseaseAssertion: monomorphic VT

FamilyInfo:NR

ParentalTesting:NR

CasePresentingHPOs:HP:0031676, HP:0033118, HP:0032643

CaseHPOFreeText: Moderately decreased right ventricular (RV) function and moderate RV dilation. moderate myocyte hypertrophy with mild to moderate interstitial fibrosis and rare adipose tissue. Cervical, mediastinal, abdominal, and pelvic FDG-avid lymphadenopathy. myocyte hypertrophy with patchy interstitial fibrosis.

CaseNotHPOs: NR

CaseNotHPOFreeText:NR

CasePreviousTesting:NR

Genotyping Method:NR

FunctionalAnalysis:NR

Variant: NM_001005242.3:c.148_151del

ClinVar: 45028

CAID: CA011079

gnomAD:NR

AdditionalInfo:NR

Case3: 39-year-old man

DiseaseAssertion: seronegative rheumatoid arthritis

FamilyInfo: Father was diagnosed with hypertrophic cardiomyopathy

ParentalTesting: Genetic testing revealed a pathogenic MYBPC3 variant in the patient and his father (c.655G>C [p.Val219Leu])

CasePresentingHPOs: HP:5210340, HP:0006682, HP:0031971

CaseHPOFreeText: Rccentric septal hypertrophy with a maximal wall thickness of 1.7 cm, no evidence of outflow tract obstruction, and an LV EF of 65% to 70%. Rare premature ventricular complexes. Mild mediastinal lymphadenopathy, pulmonary sarcoidosis

CaseNotHPOs: NR

CaseNotHPOFreeText: NR

CasePreviousTesting: NR

Genotyping Method: NR

FunctionalAnalysis: NR

Variant: NM_006252.4(PRKAA2):c.148_151del (p.Gln50fs)

ClinVar:4891957

CAID:NR

gnomAD:NR

AdditionalInfo:NR

PMID:42233912

Gene:MYBPC3, FLNC, PKP2

HGNC ID:7551, 9024, 3756

Case1: 59-year-old male

DiseaseAssertion: frequent premature ventricular contractions

FamilyInfo:Significant for dilated cardiomyopathy with multiple sudden cardiac deaths. His sister’s initial genetic testing panel was negative for pathogenic variants at that time

ParentalTesting:NR

CasePresentingHPOs: HP:0006682, HP:0025169, HP:0004751, HP:5210340

CaseHPOFreeText: Transthoracic echocardiogram (TTE) demonstrated a left ventricular (LV) ejection fraction (EF) of 20%-25% and an LV diastolic diameter of 6.6 cm. revealed bulky mediastinal adenopathy. A transbronchial biopsy of lung parenchyma showed noncaseating granulomas, and ultimately the patient was found to have pulmonary sarcoidosis.

CaseNotHPOs: NR

CaseNotHPOFreeText: NR

CasePreviousTesting:NR

Genotyping Method: NR

FunctionalAnalysis: NR

Variant:NM_001458.5(FLNC):c.4737+5G>A

ClinVar: 934656

CAID: CA1139660256

gnomAD: NR

AdditionalInfo: NR

PMID:17347475

Gene:MYOZ2

HGNC ID:1330

Case#: 33 year-old female; first cardiologic evaluation at age 24 (LV wall thickness 13 mm); re-evaluated at 33 after recurrent palpitations

DiseaseAssertion: Noonan syndrome (PTPN11) with sarcomeric hypertrophic cardiomyopathy (MYBPC3); non-obstructive HCM, mild phenotype

FamilyInfo: Father carries the MYBPC3 c.1790G>A variant and has HCM; the PTPN11 variant was absent in both parents, consistent with de novo. Both parents and the proband's brothers underwent full cardiologic evaluation, no cardiovascular disease in the other family members. Parents declined genetic testing of the underage siblings. Grandparents (I-1, I-2) and II-2, II-3 have unknown phenotypes (pedigree Fig. 2).

ParentalTesting: Both parents genotyped for the two proband variants (Table 1). Father heterozygous for MYBPC3 c.1790G>A; neither parent carries PTPN11 c.1510A>G, supporting de novo status. Phase between the two variants therefore established as in trans (different genes).

CasePresentingHPOs: HP:0001639; HP:0001962; HP:0004322; HP:0000271; HP:0001647; HP:0000508

CaseHPOFreeText: Regular psychophysical development. First echo at 24 showed mild increase in LV wall thickness (13 mm). At 33, presented with several episodes of palpitations; exam showed mild facial dysmorphisms (wide mouth, sloping forehead, prominent nasal bridge, prominent nose, low-set ears), short stature, and a systolic heart murmur. Echo: asymmetric LV hypertrophy, maximum wall thickness 16 mm at the anterior interventricular septum, mild mitral regurgitation, non-obstructive. No other cardiovascular signs.

CaseNotHPOs: HP:0001635; HP:0001650; HP:0001642; HP:0001250

CaseNotHPOFreeText: No heart failure, no LV outflow obstruction, no pulmonary stenosis, no other congenital heart defect. No intellectual disability; psychophysical development was regular. No other signs of cardiovascular disease on examination.

CasePreviousTesting: NGS panel of 325 cardiomyopathy-associated genes (Supplementary Table S1); MAF threshold 5%; variants validated by Sanger sequencing; cascade testing restricted to the two proband variants.

Genotyping Method: NGS targeted panel (Maxwell 16 DNA extraction, Agilent Alyssa analysis, Illumina Variant Interpreter, in-house pipeline) with Sanger validation; parental Sanger genotyping for the same two variants.

FunctionalAnalysis: None performed by the authors. They cite prior HeLa cell work showing the MYBPC3 c.1790G>A change causes exon 18 inclusion in the transcript and an almost undetectable 248 bp product.

Variant 1: PTPN11 NM_002834.3:c.1510A>G (p.Met504Val); heterozygous missense; de novo; classified pathogenic, explains Noonan syndrome

ClinVar: Not stated in the paper; verify the current record before submitting.

CAID: N/A

gnomAD: Not reported in the paper; I have not checked gnomAD for this variant.

Variant 2: MYBPC3 NM_000256.3:c.1790G>A (p.Arg597Gln); heterozygous missense; exon 18, last nucleotide of the exon, affecting a highly conserved residue and causing a splicing variation; inherited from the father

ClinVar: Not stated in the paper; authors note it is classified pathogenic/likely pathogenic for HCM in several genetic databases.

CAID: N/A

gnomAD: N/A

PMID: 32824488

Gene: MYBPC3

AdditionalInfo: Authors describe this as the first reported young adult with HCM and mild NS carrying variants in both PTPN11 and MYBPC3. Note the terminology problem: the abstract calls them "compound heterozygous," but the variants are in different genes on different chromosomes, so this is digenic (double heterozygosity), not compound heterozygosity. The authors argue the mild phenotype contrasts with the usual expectation that multiple sarcomeric hits worsen the disease, and that red flags justified the broad panel.

PMID: 29367541

Gene: TNNT2

HGNC ID: 11949

Case#: 64-year-old male, non-smoker, first admitted June 2014; Russian family; died 2019 at age 69

DiseaseAssertion: MYBPC3-related cardiomyopathy with a predominantly restrictive phenotype in combination with left ventricular noncompaction (LVNC) and cardiac sarcoidosis

FamilyInfo: Son (39) and daughter (35) both heterozygous for the same variant and both have non-obstructive asymmetric HCM, with no LVNC on cardiac CT; both essentially asymptomatic on beta-blocker monotherapy. Five-year SCD risk 4.82% (son) and 2.07% (daughter); ICD implanted in the son, no shocks in three years. Authors mention another family of theirs with a father who died suddenly young and children with HCM and LVNC.

ParentalTesting: Not performed; the proband is the index case; his parents were not evaluated. Transmission to both children confirmed by Sanger.

CasePresentingHPOs:HP:0001639

CaseNotHPOs: N/A

CasePreviousTesting: N/A

Genotyping Method: Next-generation sequencing panel; variants confirmed by Sanger.

FunctionalAnalysis: N/A

Variant 1: MYBPC3 NM_000256.3:c.278delA; heterozygous frameshift

Variant 2: KCNJ5 c.464G>A; heterozygous missense

ClinVar: N/A

CAID:N/A

gnomAD: N/A

Gene:MYBPC3

PMID:36011256

PMID : 40008267

Gene: TNNT2

HGNC ID: 11949

Case1: gestational age 40 weeks female

DiseaseAssertion: Poor feeding, cyanosis, and difficulty with breathing.

FamilyInfo: Healthy non‐consanguineous parents. Echocardiographic in the mother and sister were normal. Father had mild dilatation of the left atrium with an abnormal flow pattern in the mitral valve, otherwise healthy.

ParentalTesting: c.2373_2374insG mutation found in the mother

CasePresentingHPOs:HP:0025169,

CaseHPOFreeText: hypertrophic non‐obstructive cardiomyopathy with poor left and right ventricular systolic function. The left ventricular end diastolic diameter measured 17.3 mm (99% of normal), end systolic diameter 12.9 mm (116% of normal), and left ventricular posterior wall 3.6 mm (111% of normal). The intraventricular septum measured 11.8 mm (288% of normal). The shortening fraction of the left ventricle was decreased to 25%. Multiple abnormal small communications with a minimal flow between a coronary artery and the right ventricle were observed in the apical portion of the interventricular septum. There were no structural congenital heart defects.

CaseNotHPOs: NR

CaseNotHPOFreeText: NR

CasePreviousTesting: NR

Genotyping Method:

FunctionalAnalysis: NR

Variant: NM_006073.4(TRDN):c.1624+1G>A

ClinVar:2152664

CAID: CA147231745

gnomAD:NR

AdditionalInfo:NR

PMID: 16679492

Gene: MYBPC3

HGNC ID:7551

Case1: 48 year old male

DiseaseAssertion: . Two missense variants in MYBPC3 (NM_000256.3): c.2533C>G in exon 26 (C6 domain) were identified and, classified as a variant of uncertain significance (VUS, score 2), and c.1696T>A in exon 18 (C4 domain), a VUS with a score of 5.

FamilyInfo: There was no family history of cardiomyopathy or SCD.

ParentalTesting: NR

CasePresentingHPOs: HP:0004751, HP:0006682, HP:0001712

CaseHPOFreeText: 38 year old man, suffering from contractions, and one short run of non-sustained ventricular tachycardia lasting four beats. Asymmetric septal hypertrophy with a maximum thickness of 19 mm. In addition, marked biatrial enlargement was evident, with a left atrial volume index of 79 mL/m² and right atrial area of 25 cm². Importantly, extensive diffuse late gadolinium enhancement (LGE) was detected in the basal and mid-septal and anterior segments, involving 17% of the myocardial mass

CaseNotHPOs: NR

CasePreviousTesting: genetic testing was performed using the Health in Code HCM panel, which includes the following 18 genes: ACTC1, DES, FHL1, FHOD3, GLA, LAMP2, MYBPC3, MYH7, MYL2, MYL3, PRKAG2, PTPN11, TNNC1, TNNI3, TNNT2, TPM1, TRIM63, and TTR.

Genotyping Method: Health in Code HCM panel

FunctionalAnalysis:

Variant: NM_000256.3:c.2533C>G, NM_000256.3:c.1696T>A

ClinVarID:180973, 915724

CAID:CA380324353, CA012504

gnomAD:

AdditionalInfo:NR

PMID: 28815794

Gene: TNNT2

HGNC ID: 11949

PMID: 20641121

Gene: MYL3

HGNC ID: HGNC:7584

Case#: 30 year old female athlete

DiseaseAssertion: Subclinical hypertrophic cardiomyopathy

FamilyInfo: Her mother has HCM and the same ACTC1 gene change. Her grandmother and uncle on her mothers side died suddenly.

ParentalTesting: Her mother tested positive for the ACTC1 gene change and there isn't any information about the father.

CasePresentingHPOs: NR

CaseHPOFreeText: The patient did not have dizziness, fainting, trouble breathing or chest pain. Her heart muscle was not thickened.

CaseNotHPOs: NR

CaseNotHPOFreeText: The patient sometimes felt her heart beating unusually during exercise. A heart MRI showed small changes in her heart muscle and heart valve.

CasePreviousTesting: The patient had an ECG, heart ultrasound, heart monitor and heart MRI

Genotyping Method:Sanger sequencing was used to test the ACTC1 gene.

FunctionalAnalysis: NR

Variant: ACTC1 p.Val11Leu

Clinvar: 2947021

CAID: CA391633409

gnomAD: NR

AdditionalInfo: The patient continued playing competitive sports and had regular heart checkups.

Whole genome sequencing in paediatric channelopathy and cardiomyopathy

PMID: 38586174 Gene: MYBPC3 HGNC ID: 7551

Case2: 12-year-old boy (Patient 2) DiseaseAssertion: DCM FamilyInfo: Family history unremarkable. ParentalTesting: The MYBPC3 variant was inherited from his father. The father’s cardiac phenotype is not reported. CasePresentingHPOs: HP:0001644, HP:0003546 CaseHPOFreeText: Severely depressed biventricular function; heart transplantation for decompensated heart failure. CaseNotHPOs: CaseNotHPOFreeText: CasePreviousTesting: Previous WES was negative; the variant’s intronic region was not adequately covered. Genotyping Method: Whole-genome sequencing (WGS; Illumina NovaSeq 6000; aligned to hg19/GRCh37). FunctionalAnalysis: SpliceAI predicted a potential splicing effect; no functional assay in this patient is reported. Variant: NM_000256.3:c.1224-80G>A (heterozygous intronic variant) ClinVar: 693982 CAID: CA221697326 gnomAD: 0.0000637 AdditionalInfo: The authors classified the variant as a VUS in this DCM case because evidence for a MYBPC3–DCM relationship is limited. ClinVar currently reports a pathogenic/likely pathogenic aggregate classification, primarily in relation to HCM. Reanalysis found no second MYBPC3 variant.

PMID: 22194935

Gene: MYBPC3

HGNC ID: HGNC:7551

PMID 37498360

Gene: TPM1

HGNC ID: 12010

Case1: HCM patient-derived cell line UKEi070-A (demographics not reported in this paper) DiseaseAssertion: HCM

ParentalTesting: CasePresentingHPOs: HP:0001639 CaseHPOFreeText: CaseNotHPOs: CaseNotHPOFreeText: CasePreviousTesting: Genotyping Method: Not reported in this paper; it references a previously established patient-derived cell line. FunctionalAnalysis: The variant is reported to cause MYBPC3 protein haploinsufficiency in cardiomyocytes. In this study, TTL overexpression normalized cell hypertrophy in the HCM cell model. Variant: NM_000256.3:c.2308G>A (heterozygous; the paper reports the splice consequence as p.Asp770Serfs98X) ClinVar: 36604 CAID: gnomAD: NR AdditionalInfo: The paper uses patient-derived induced pluripotent stem cell cardiomyocytes; it does not provide the patient’s age, sex, or pedigree.

Chronic Activation of Tubulin Tyrosination Improves Heart Function

PMID: 39279670 Gene: MYBPC3 HGNC ID: 7551

Novel Intragenic PAX6 Deletion in a Pedigree with Aniridia, Morbid Obesity, and Diabetes

PMID: 31361967

Gene: MYBPC3

HGNC ID: 7551

Case1: 50 year old male DiseaseAssertion: HCM; hydroxychloroquine cardiotoxicity FamilyInfo: Six children undergoing predictive testing for the familial MYBPC3 variant; family history not reported ParentalTesting: CasePresentingHPOs: HP:0001639 CaseHPOFreeText: Monomorphic ventricular tachycardia, dyspnea, nausea, vomiting, biventricular hypertrophy, systolic dysfunction, cardiogenic shock CaseNotHPOs: CaseNotHPOFreeText: CasePreviousTesting: Prior CMR showed nonobstructive HCM; cardiomyopathy gene panel identified the variant Genotyping Method: Cardiomyopathy gene panel FunctionalAnalysis: Altered splicing with exon 30 skipping; authors describe a nonfunctional protein or premature stop codon Variant: c.3330+5G>C ClinVar: 42706 CAID: gnomAD: 0.03% (as reported in the article) AdditionalInfo: Long-term hydroxychloroquine exposure for malaria prophylaxis; biopsy findings were consistent with both HCM and hydroxychloroquine cardiotoxicity

Hydroxychloroquine Cardiotoxicity and Sarcomeric Hypertrophic Cardiomyopathy.”

PMID: 40514126 Gene: MYBPC3 HGNC ID: 7551

PMID: 30279906

Gene: TNNI3

HGNC ID: 11947

PMID: 31293105

Gene: MYBPC3

HGNC ID: HGNC:7551

PMID: 32453731

Gene: MYL2

HGNC ID: 7583

Case1: Male, Infant, Tunisian

DiseaseAssertion: infantile-onset HCM and mitral valve dysplasia

FamilyInfo: Family with consanguinity in which four children had died before one year of age. The father (37 years old) and mother (27 years old) of the proband are consanguineously related. Two infants (VI:1 and VI:2) died at less than 30 days of age from cardiorespiratory arrest, and two (VI:3 and VI:4, proband) of them displayed abnormal cardiac findings on chest roentgenogram. While all four children displayed hepatomegaly and general hypotonia, VI:3 and VI:4 had a marked increase in heart size and died from refractory cardiogenic shock. The status of the MYL2 allele in siblings is unknown. The proband (fs/fs) was homozygous for the MYL2-fs allele while the parents were found to be heterozygous (fs/wt) carriers. The father (37 years old) and mother (27 years old) of the proband are consanguineously related, were asymptomatic from a cardiac standpoint and had normal cardiac anatomy and function as evaluated by an echocardiogram

ParentalTesting: Homozygous variant in the proband and that the parents are heterozygous carriers using Sanger DNA sequencing of the genomic region. Father (37 years old) and mother (27 years old) were asymptomatic from a cardiac standpoint and had normal cardiac anatomy and function as evaluated by an echocardiogram

CasePresentingHPOs: HP:0200128, HP:0001653, HP:0002092, HP:0001639, HP:0002240

CaseHPOFreeText: Showed a rapid decline in health and was treated for various periods in neonatal intensive care units. The patient also displayed severe mitral valve regurgitation with abnormal thickening of the mitral valve leaflets and pulmonary arterial hypertension. Post-mortem examination of the proband’s heart confirmed severe biatrial dilatation, significant biventricular hypertrophy with small ventricular cavities and severe mitral valve dysplasia

CaseNotHPOs: NR

CaseNotHPOFreeText: no gross developmental defects

CasePreviousTesting: No prior genetic testing reported before exome sequencing

Genotyping Method: Performed exome sequencing on the proband. Exome libraries were constructed using the Agilent SureSelectQXT Target Enrichment System for Illumina Multiplexed Sequencing Protocol (Agilent Technologies, CA). DNA libraries were captured with the Agilent Clinical Research Exome Kit. Paired-end 150 base pair reads were generated for exome-enriched libraries sequenced on the Illumina HiSeq 4000 to a targeted depth of 100× coverage

FunctionalAnalysis: Functional analysis performed. Immunohistochemical analysis of MYL2 expression in the proband’s ventricular myocardium shows a remarkable reduction in the expression of MYL2 as compared to control. Also, MYL2 mRNA was detected in the ventricle of the proband by RT-PCR. This suggests that the frameshift variant adversely affects the levels of MYL2 protein in the proband. Using immunoblot analysis, we observed that overexpression of the MYL2-fs variant was significantly reduced compared to stop-gain variants and the missense variant. When the H9c2 cells were treated with MG-132 after transfection with the MYL2-fs construct, the GFP signal corresponding to MYL2-fs was recovered. The in vitro experiments indicate that the MYL2-fs variant is not stable and that proteasome-mediated degradation of the translated product plays a key role in the instability of the protein. The overexpression of the fs variant identified in our proband or the MYL2-G162R missense variant failed to rescue the phenotype. Results reported in Figures 2, 3, and 4.

Variant: NM_000432.3:c.431_432delCT

ClinVar: NR

CAID: UnregisteredVariant

gnomAD: NR

AdditionalInfo: 4 siblings who died before 1 year of age but MYL2 genotyping was only confirmed in the proband (VI:4)

Case#: Deceased child, female; age 5.5 months

DiseaseAssertion: Hypertrophic cardiomyopathy with endomyocardial fibroelastosis

FamilyInfo: The mother carried c.2373dup, and the father carried c.592G>T.

ParentalTesting: The mother carried c.2373dup, and the father carried c.592G>T.

CasePresentingHPOs: HP:0001706 HP:0200128 HP:0012664 HP:0002094 HP:0000961

CaseHPOFreeText: Acute heart failure; massive biventricular cardiac enlargement; biventricular dysfunction; progressive dyspnea; blue lips; pale appearance; endocardial fibrosis; cardiopulmonary arrest.

CaseNotHPOFreeText: No congenital heart disease or valve abnormalities were found at autopsy

Genotyping Method: Postmortem molecular testing

Variant: MYBPC3 c.592G>T (p.Asp198Tyr); missense

MYBPC3 c.2373dup, p.Trp792Valfs*41); frameshift duplication

ClinVar: c.592G>T: NR; c.2373dup: 42619

CAID: c.592G>T: NR; c.2373dup: CA012139

gnomAD: c.592G>T was not observed in more than 123,000 individuals; c.2373dup: 0.0017% overall

AdditionalInfo: The child died from severe early-onset cardiac disease at 5.5 months. Autopsy showed endomyocardial fibroelastosis and severe biventricular involvement.

PMID: 35029218

Gene: TPM1

HGNC ID: 12010

Case#: Family B, Case IV.2; 8-year-old male; diagnosed at age 6

DiseaseAssertion: Dilated cardiomyopathy (DCM)

FamilyInfo: Positive family history of sudden cardiac death (SCD). The proband's brother (IV.1) died at age 2 of SCD and renal failure. Both parents (III.1 and III.2) were asymptomatic heterozygous carriers of MYL3 c.106G>T. Two unaffected siblings were tested: IV.3 was wild-type and IV.4 was heterozygous (Fig. 1b; Supplementary Fig. S2b).

ParentalTesting: Both parents (III.1 and III.2) were confirmed heterozygous carriers of MYL3 c.106G>T by PCR and bidirectional Sanger sequencing, supporting autosomal recessive inheritance (Supplementary Genetic Findings; Fig. S2b).

CasePresentingHPOs: HP:0001644 (Dilated cardiomyopathy); HP:0000085 (Horseshoe kidney); HP:0005162 (Reduced left ventricular ejection fraction).

CaseHPOFreeText: DCM diagnosed at age 6; heart transplantation performed shortly after diagnosis. Clinical evaluation revealed horseshoe kidney, severe left ventricular dysfunction (LVEF 15–20%), moderate right ventricular dysfunction (TAPSE 9 mm), chamber cardiomegaly on coronary CT angiography, and rapid ventricular tachycardia on ECG (Main text, Family B; Supplementary Results, p. 6).

CaseNotHPOs: NR

CaseNotHPOFreeText: NR

CasePreviousTesting: NR (no prior diagnostic genetic testing reported before the study's exome sequencing)

Genotyping Method: Exome sequencing identified the homozygous MYL3 c.106G>T (p.Glu36Ter) variant in the proband (IV.2). PCR and bidirectional Sanger sequencing validated the variant and confirmed segregation in the parents and two unaffected siblings (Supplementary Methods; Supplementary Genetic Findings; Fig. S2b).

FunctionalAnalysis: Zebrafish cmlc1 knockdown and rescue experiments were performed using human MYL3 RNA containing c.106G>T (p.Glu36Ter). Unlike wild-type MYL3 RNA, the mutant RNA failed to rescue the cardiac phenotype, with persistent cardiac edema, ventricular dysfunction, and atrial dilation (Fig. 2; Supplementary Methods; Supplementary Movie S7).

Variant: MYL3 NM_000258.2:c.106G>T (p. Glu36Ter); homozygous nonsense variant

ClinVar: NR

CAID: CA352499542

gnomAD: NR

AdditionalInfo: The authors classified the homozygous MYL3 c.106G>T (p.Glu36Ter) nonsense variant as pathogenic. The variant introduces a premature termination codon at amino acid 36. The proband was born to asymptomatic, consanguineous (first-cousin) parents of Bakhtiyari ancestry. Family segregation and zebrafish functional studies provide supporting evidence (Supplementary Results; Supplementary Genetic Findings; Supplementary Table S2).

Case#: Family C, Case VI.1; female; diagnosed at age 2.5 years; died at age 8

DiseaseAssertion: Unclassified cardiomyopathy

FamilyInfo: Family C has a positive family history of childhood-onset cardiomyopathy and sudden cardiac death. The affected individual (VI.1) was diagnosed with cardiomyopathy at age 2.5 years and died at age 8. Three maternal relatives (V.5, V.6, and V.8) are depicted as affected and deceased in the pedigree (Fig. 1C). Both parents (V.1 and V.2) were clinically unaffected heterozygous carriers of the MYL3 c.482-1G>A splice-acceptor variant. The genotype of VI.1 could not be confirmed because DNA was unavailable.

ParentalTesting: PCR and bidirectional Sanger sequencing confirmed that both parents (V.1 and V.2) were heterozygous carriers of MYL3 c.482-1G>A. Direct testing of the affected daughter (VI.1) was not possible because DNA was unavailable. Her homozygous genotype was therefore suspected but not confirmed (Fig. 1C; Supplementary Genetic Findings).

CasePresentingHPOs: HP:0001638 (Cardiomyopathy); HP:0001645 (Sudden cardiac death).

CaseHPOFreeText: Female diagnosed with unclassified cardiomyopathy at age 2.5 years; died of sudden cardiac death at age 8 (Family C, Fig. 1C).

CaseNotHPOs: NR (no patient-specific negative HPO findings confirmed for VI.1).

CaseNotHPOFreeText: The authors reported no evidence of muscle weakness by neurological examination or history among affected individuals from the three families; however, it is unclear whether this assessment specifically included VI.1.

CasePreviousTesting: NR (no prior genetic testing reported for VI.1).

Genotyping Method: Genetic analysis of the affected individual's mother (V.2) identified MYL3 c.482-1G>A. PCR and bidirectional Sanger sequencing validated the variant and confirmed both parents (V.1 and V.2) as heterozygous carriers. VI.1 was not directly genotyped because DNA was unavailable (Supplementary Genetic Findings; Fig. 1C and S2C).

FunctionalAnalysis: A minigene splicing assay in human HEK293FT cells demonstrated that MYL3 c.482-1G>A causes abnormal RNA splicing. The predominant outcome (~75%) was skipping of the 78-bp exon 5, producing an in-frame deletion (p.Gly161_Glu186del). A less frequent outcome (~25%) was deletion of the first nucleotide of exon 5, causing a frameshift (p.Gly161Valfs*4). Both outcomes are predicted to disrupt EF-hand domains. The authors note that the minigene assay may not fully reflect in vivo splicing frequencies (Supplementary Results, pp. 7–8; Fig. 2E–I).

Variant: MYL3 c.482-1G>A (rs727503300)

ClinVar: 164486

CAID: CA013932

gnomAD: NR MYL3 c.482-1G>A was not found in the gnomAD v4 (GRCh38) region results at chr3:46,860,813. Allele frequency not reported for this variant in the searched dataset.

AdditionalInfo: The affected individual (VI.1) died at age 8, and DNA was unavailable for direct genetic testing. Both clinically unaffected parents (V.1 and V.2) were confirmed heterozygous carriers of MYL3 c.482-1G>A, suggesting that VI.1 may have inherited the variant from both parents; however, her genotype remains unconfirmed. A minigene assay demonstrated that the variant disrupts RNA splicing, predominantly causing exon 5 skipping, with a less frequent frameshift-producing splicing event. These functional findings support a damaging effect of the variant but do not establish VI.1's genotype (Fig. 1C; Fig. 2E–I; Supplementary Genetic Findings and Minigene Assay Results).

Case#: Family A, Case III.7; 38-year-old female; diagnosed at age 26

DiseaseAssertion: Hypertrophic cardiomyopathy (HCM)

FamilyInfo: Positive family history of HCM and SCD. Mother (II.4), brother (III.8), uncle (II.7), and cousin (III.11) died of SCD at ages 55, 26, 57, and 24, respectively. The proband's three children (IV.3, IV.4, IV.5) were homozygous for the MYL3 variant but had normal echocardiograms at ages 18, 13, and 6.

ParentalTesting: Supplementary Table S2 reports parental testing supportive of PM3 (variants in trans). However, DNA was unavailable for the proband's deceased mother (II.4), and individual parental genotypes were not specified in the supplementary genetic findings.

CasePresentingHPOs: HP:0001639 (Hypertrophic cardiomyopathy); HP:0002094 (Dyspnea); HP:0001653 (Mitral regurgitation); HP:0001712 (Left ventricular hypertrophy)

CaseHPOFreeText: HCM diagnosed at age 26 following dyspnea. At age 38, echocardiography showed reverse-curvature HCM with asymmetric left ventricular hypertrophy involving anterior, anterolateral, and lateral segments; maximum wall thickness 22 mm; severe mitral regurgitation; LVEF 55%; E/e' ratio 16.4; resting LVOT gradient 9 and post-maneuver gradient 30. Holter monitoring showed no arrhythmias (Supplementary Results, pp. 5–6; Table S1; Fig. S1).

CaseNotHPOs: HP:0001324 (Muscle weakness)

CaseNotHPOFreeText: Neurological evaluation revealed normal muscle tone, strength 5/5 in upper and lower limbs, no distal or proximal muscle atrophy or fasciculations, and normal creatine phosphokinase levels.

CasePreviousTesting: Exome sequencing was performed; no rare, likely pathogenic variants in other cardiomyopathy-associated genes identified after filtering.

Genotyping Method: Exome sequencing identified the MYL3 variant; bidirectional Sanger sequencing validated the variant. Familial genotyping supported recessive inheritance (Fig. 1a).

FunctionalAnalysis: Zebrafish cmlc1 knockdown and rescue experiments were performed using human MYL3 RNA carrying c.170C>A (p.Ala57Asp). Mutant RNA showed partial phenotypic rescue but no statistically significant improvement in ventricular contractility compared with knockdown alone (Fig. 2a-d).

Variant: MYL3 NM_000258.2:c.170C>A (p.Ala57Asp); homozygous missense variant; rs139794067

ClinVar: 43121

CAID: CA013575

gnomAD: Allele frequency 0.000163 (0 homozygotes), as reported in Supplementary Table S2.

AdditionalInfo: Family A, Case III.7. Clinical characteristics and genetic findings described in the Results section (Fig. 1a and 1d-e). Functional experiments described in Fig. 2. The authors classified c.170C>A as a variant of uncertain significance (VUS).

PMID: 33288880

Gene: MYL3

HGNC ID: 7584

Case#: Female, Hispanic, 4

DiseaseAssertion:Dilated cardiomyopathy

FamilyInfo: Uncle who died at a young age of sudden cardiac death.

ParentalTesting:

CasePresentingHPOs: HP:0001638

"severe decompensated cardiomyopathy at age 4."

CaseHPOFreeText: NR

CaseNotHPOs: NR

CaseNotHPOFreeText:NR

CasePreviousTesting: NR

Genotyping Method: commercial genetic testing and Sanger sequencing

FunctionalAnalysis:

Variant: NM_001276345.2:c.*187C>T

ClinVar: NR

CAID:CA2649785730

gnomAD:NR

AdditionalInfo:

PMID: 26498512

Gene: TNNT2

HGNC ID: 11949

Case#: Family #6; 36-year-old male

DiseaseAssertion: Arrhythmogenic right ventricular cardiomyopathy (ARVC); diagnosed according to the 2010 revised Task Force Criteria

FamilyInfo: Family #6. No informative segregation evidence specifically linking the MYL3 variant to ARVC was reported. The authors noted that family screening was incomplete or normal in other families, but did not specify which circumstance applied to Family #6.

ParentalTesting: NR

CasePresentingHPOs: HP:0006682 (PVCs)

CaseHPOFreeText: Symptomatic presentation; major right ventricular structural abnormality; minor ECG repolarization criterion; 1,181 ventricular ectopic beats on Holter monitoring; sustained ventricular arrhythmia (specific rhythm not reported).

CaseNotHPOs: HP:0001279 (Syncope); HP:0005162 (Abnormal left ventricular function)

CaseNotHPOFreeText: No cardiac syncope or left ventricular dysfunction reported. Absence of cardiac syncope does not necessarily exclude every form of syncope.

CasePreviousTesting: No pathogenic or likely pathogenic variants identified in established ARVC-associated genes (PKP2, DSG2, DSP, DSC2, JUP, TMEM43, PLN, SCN5A). Subsequent screening included nine sarcomere genes: ACTC1, MYBPC3, MYH7, MYL2, MYL3, TNNC1, TNNI3, TNNT2, and TPM1. The study used broad genetic testing, including whole-exome sequencing in a subset of probands; whether Family #6 underwent whole-exome sequencing was not specified.

Genotyping Method: Sarcomere-gene sequencing and deletion/duplication analysis through clinical cardiomyopathy panels, research-based next-generation sequencing panels, or whole-exome sequencing. The exact initial platform for Family #6 was not specified. Identified variants were confirmed by PCR amplification and Sanger sequencing.

FunctionalAnalysis: NR

Variant: MYL3 NM_000258.2:c.461G>A (p.Arg154His); missense variant; exon 4

ClinVar: 14062

CAID: CA013861

gnomAD: MYL3 c.461G>A (p.Arg154His), GRCh38: 3-46859495-C-T. gnomAD v4: Exome AF = 0.00003557; Genome AF = 0.00001971; Total AF = 0.00003408. European (non-Finnish): AC = 52, AF = 0.00004407. https://gnomad.broadinstitute.org/variant/3-46859495-C-T?dataset=gnomad_r4

AdditionalInfo: Murray et al. (2018), Tables 1 and 2, Family #6. The MYL3 variant was classified as likely pathogenic (LP) according to ACMG criteria, with a PolyPhen-2 score of 0.861. The proband met criteria for definite ARVC, with no reported left ventricular dysfunction. Although the variant was rare and computationally predicted to be damaging, the authors emphasized that evidence demonstrating a causal relationship between sarcomere variants and ARVC remained insufficient. No direct functional analysis of this variant was performed in the study.

PMID: 29709087

Gene: MYL3

HGNC ID: 7584

PMID: 28538763

Gene: TNNT2

HGNC ID: 11949

Case#: Male, 17

DiseaseAssertion: hypertrophic cardiomyopathy

FamilyInfo: All family members were asymptomatic, with normal TTE and ECG, with no evidence of VH.

ParentalTesting:

CasePresentingHPOs: HP:0001639, HP:0001279, HP:0001670, HP:0032092, HP:0031295

CaseHPOFreeText: diastolic type II dysfunction,

CaseNotHPOs: NR

CaseNotHPOFreeText: NR

CasePreviousTesting: genetic analysis of the proband was performed through direct sequencing of the three sarcomere genes: MYH7, MYBPC3 and TNNT2

Genotyping Method: Sanger Sequencing

FunctionalAnalysis: NR

Variant: NR

ClinVar:NR

CAID: NR

gnomAD: NR

AdditionalInfo: underwent clinical and cardiovascular examination, including a 12-lead electrocardiogram (ECG), transthoracic echocardiography (TTE) and 24-hour Holter monitoring. TNNT2 sequenced, but not reported.

Case#: Female, 4 months, Swedish

DiseaseAssertion: dilated cardiomyopathy

FamilyInfo: Strong family history of DCM and faily history of SCD due to DCM. Maternal grandfather had enlarged left ventricle.

ParentalTesting:

CasePresentingHPOs: HP:0005162, HP:0031295, HP:0001653,

CaseHPOFreeText: enlarged left ventricle,

CaseNotHPOs:HP:0011947

CaseNotHPOFreeText: circulatory collapse

CasePreviousTesting: NR

Genotyping Method: Sanger sequencing

FunctionalAnalysis: NR

Variant: NM_001276345.2:c.548G>A

ClinVar:43649

CAID: CA004727

gnomAD:NR

AdditionalInfo: During cardiac catheterization, cardiac resuscitation due to circulatory collapse was needed.

PMID: 28669108

Gene: TNNT2

HGNC ID: 11949

PMID: 30923642

Gene: TPM1

HGNC ID: 12010

PMID: 27141495

Gene: TNNT2

HGNC ID: 11949

PMID: 27199119

Gene: TNNT2

HGNC ID: 11949

PMID: 31770195

Gene: TNNT2

HGNC ID: 11949

Case#: Female, 6 months

DiseaseAssertion: Dilated cardiomyopathy

FamilyInfo: Mother was age 40 at time of birth, which is a high-risk factor for birth defects

ParentalTesting:

CasePresentingHPOs: HP:0031664, HP:0010438, HP:0005162

CaseHPOFreeText: blood pressure of the four limbs was "92/44 mmHg at the right upper limb, 96/58 mmHg at the left upper limb, 101/60 mmHg at the right lower limb, and 103/54 mmHg at the left lower limb." Enlarged heart boundaries. Shifted apex.

CaseNotHPOs: HP:0000975

CaseNotHPOFreeText: decreased milk consumption

CasePreviousTesting: NR

Genotyping Method: genomic sequencing.

FunctionalAnalysis: NR

Variant: NM_001276345.2:c.548G>A

ClinVar:43649

CAID:CA004727

gnomAD: NR

AdditionalInfo:

PMID: 35004917

Gene: TPM1

HGNC ID: 12010

Case1: Male, 37 years old, Colombian

DiseaseAssertion: asymmetric septal hypertrophic cardiomyopathy

FamilyInfo: During genetic assessment, a family history of hypertrophic cardiomyopathy (HCM) was detected. The patient’s mother had HCM and died at the age of 66; two living brothers have HCM (51 and 60 years of age). In addition, two of his brothers under the age of 35 died suddenly, two more brothers died from an unknown cause before the age of 5, and yet another brother is being examined for possible heart disease. Findings indicated a dominant inheritance pattern for HCM in this family. Pedigree shown in Figure 2.

ParentalTesting: NR

CasePresentingHPOs: HP:0001639, HP:0001663, HP:0001962, HP:000209, HP:0002315

CaseHPOFreeText: At the age of 25, his symptomatology started, including intense fatigue and mild thoracic pain due to physical activity. At the age of 32, an echocardiogram revealed asymmetric septal hypertrophic cardiomyopathy. The thickness of the interventricular septum was 19.5 mm in the basal third, 22 mm in the middle third, and 23 mm in the apical third, and ventricular tachycardia was also present. Alcohol septal ablation was performed. However, ventricular tachycardia and disabling symptoms persisted, so he required an implantable cardioverter-defibrillator at the age of 35. A routine echocardiogram at the age of 36 yielded the following findings: an LV of normal size, mild hypertrophy of the septum, normal systolic function, and diastolic dysfunction with slow LV relaxation. The patient still suffers dyspnea during physical effort and occasionally thoracic pain with palpitations

CaseNotHPOs: NR

CaseNotHPOFreeText: NR

CasePreviousTesting: NR

Genotyping Method: A molecular panel for HCM including 17 genes was performed using next-generation sequencing. Sanger sequencing chromatogram focusing on the targeted region including the variation

FunctionalAnalysis: NR

Variant: NM_000432.3:c.260G>C

ClinVar: 43461

CAID: CA009968

gnomAD: NR

AdditionalInfo: NR

PMID: 33139982

Gene: MYL2

HGNC ID: 7583

PMID: 21823217

Gene: MYL3

HGNC ID: 7584

Case#: Patient 1, individual II.1 (Fig. 2A); 22-year-old Salvadoran female

DiseaseAssertion: Restrictive cardiomyopathy (RCM) with advanced heart failure

FamilyInfo: Patient denied a family history of cardiomyopathy, although supporting records were unavailable. Her mother (I.2) was clinically unaffected at age 45 and heterozygous for both MYL3 p.Glu143Lys and MYL2 p.Gly57Glu. Other family members were unavailable for evaluation (Fig. 2A; Table I).

ParentalTesting: Mother (I.2) was confirmed heterozygous for MYL3 c.427G>A (p.Glu143Lys) and MYL2 c.170G>A (p.Gly57Glu). Paternal testing was not reported.

CasePresentingHPOs: HP:0012764 (Orthopnea); HP:0004749 (Atrial flutter); HP:0031295 (Left atrial enlargement); HP:0030718 (right atrial enlargement)

CaseHPOFreeText: Worsening fatigue and exertional dyspnea over 12 months, paroxysmal nocturnal dyspnea, palpitations, NYHA Class III–IV heart failure, and ascites suggestive of congestive hepatopathy. Echocardiography showed severe biatrial enlargement and advanced left ventricular diastolic dysfunction with preserved systolic function. Additional findings included myocardial fibrosis and myofiber disarray on biopsy.

CaseNotHPOs: NR

CaseNotHPOFreeText: At initial presentation, patient denied dizziness, syncope, and lower-extremity edema. No S4 heart sound was detected. Recurrent syncope developed later.

CasePreviousTesting: Targeted sequencing of eight sarcomere genes (ACTC, MYBPC3, MYH7, MYL2, MYL3, TNNI3, TNNT2, TPM1). Genome-wide analysis was not reported. An additional heterozygous MYL2 variant, c.170G>A (p.Gly57Glu), was identified (ClinVar Variation ID: 43458; CAID: CA009910).

Genotyping Method: Sequencing of coding exons and intron–exon boundaries of MYL3 and seven additional sarcomere genes, performed by a commercial CLIA-certified laboratory (Correlagen Diagnostics, Inc.). The specific sequencing platform was not reported.

FunctionalAnalysis: NR

Variant: MYL3 NM_000258.2:c.427G>A (p.Glu143Lys); homozygous

ClinVar: 14063

CAID: CA013774

gnomAD: MYL3 c.427G>A (p.Glu143Lys). Highest reported ancestry-specific allele frequency: 0.0002333 (0.02333%) in the Admixed American population (AC = 14). Overall AF (exomes): 0.000008209; AF (genomes): 0.00001314; AF (total): 0.000008674. https://gnomad.broadinstitute.org/variant/3-46859529-C-T?dataset=gnomad_r4.

AdditionalInfo: Patient developed recurrent syncope and received an implantable cardioverter-defibrillator. She underwent orthotopic heart transplantation six months after RCM diagnosis. Authors considered the homozygous MYL3 and heterozygous MYL2 variants likely contributors to disease, although their individual contributions were not established. Clinical and family findings are reported in Patient 1, Figure 2A, and Table I.

PMID: 36613463

Gene: TPM1

HGNC ID: 12010

Case#: Japanese female

DiseaseAssertion: Mild cardiac hypertrophy and asymmetric septal hypertrophy with myocardial hypertrophy increasing.

FamilyInfo: mother and grandmother showed phenotype. Probands mother has the Arg92Trp mutation of TNNT2.

ParentalTesting:not reported

CasePresentingHPOs: HP:0001670

CaseHPOFreeText: not reported

CaseNotHPOs:not reported

CaseNotHPOFreeText:not reported

CasePreviousTesting: DNA analysis

Genotyping Method: Patients with familial HCM

FunctionalAnalysis:not reported

Variant:NM_001276345.2:c.107A>T

ClinVar:not reported

CAID:CA344207376

gnomAD:not reported

AdditionalInfo: pedigree and phenotype associated with Family C.

PMID: 29914921

Gene: MYL3

HGNC ID: 7584

Case#: Single proband ; 63-year-old female; palpitations at presentation July 2025; HCM diagnosis established at age 63

DiseaseAssertion: Hypertrophic cardiomyopathy (HCM) complicated by apical left ventricular aneurysm and mid-ventricular obstruction⁠

FamilyInfo: No family history of cardiac disease or sudden cardiac death at a young age reported. Both parents deceased (one of cancer, one of natural causes at age 92), neither with reported cardiovascular disease; proband has no siblings. Only first-degree relative is her son, who carries the KCNJ5 c.464G>A variant but not the MYBPC3 c.278delA variant, and has a normal echocardiogram with no myocardial hypertrophy. No pedigree beyond the son (Fig. 3B).⁠

ParentalTesting: Not performed; both parents deceased, no DNA available; authors state a valid familial segregation analysis could not be performed. Only one family member (son) was available for cascade Sanger screening.⁠

CasePresentingHPOs: HP:0001639 (Hypertrophic cardiomyopathy); HP:0001649 (Tachycardia), palpitations; HP:0001712 (Left ventricular hypertrophy).

CaseNotHPOFreeText: No history of hypertension, diabetes, or hyperlipidemia. Phenocopies excluded: no extra-cardiac manifestations of Fabry disease and GLA testing negative; cardiac amyloidosis excluded (no apical sparing, normal serum free light chains, negative serum protein electrophoresis and immunofixation); no significant coronary stenosis on coronary CT angiography. No QT prolongation or features of Andersen–Tawil syndrome on ECG.

CasePreviousTesting: Whole exome sequencing identified both variants; all rare and known variants validated by Sanger sequencing, with cascade Sanger screening in available one family member. No prior genetic testing reported before this episode.

Genotyping Method: Targeted region capture with next-generation high-throughput sequencing (whole exome, exonic plus flanking regions); variants confirmed by bidirectional Sanger sequencing. Cascade screening by Sanger in the son. MYBPC3 variant absent from 1000 Genomes, ESP6500, ExAC, and the Besuper local database. KCNJ5 variant absent from 1000 Genomes and ESP6500, ExAC frequency, absent from local Basenhall controls.⁠

FunctionalAnalysis: None performed; authors list absence of functional studies and lack of mRNA-level validation as limitations. MYBPC3 frameshift predicted to trigger nonsense-mediated decay.⁠

Variant: MYBPC3 NM_000256.3:c.278delA (p.Lys93ArgfsTer3); heterozygous; exon 2; novel, not in ClinVar or HGMD; classified Likely Pathogenic by ACMG (PVS1, PM2). Second variant: KCNJ5 NM_000256.3:c.464G>A (p.Arg155Gln); heterozygous; exon 2; novel, not in ClinVar or HGMD; classified VUS (PM2, PP3). Note the paper's KCNJ5 accession is written as NM_000256.3, which is the MYBPC3 transcript, most likely a typo in the article Pepper please conform for me the correct KCNJ5 accession

ClinVar: No ClinVar record for either variant; nearby KCNJ5 missense variants c.451G>A, c.452G>A, c.470T>G, and c.473C>G are documented as pathogenic/likely pathogenic for long QT syndrome or aldosteronism, and downstream frameshift/nonsense variants at the MYBPC3 locus are classified pathogenic or likely pathogenic.

CAID:Not found.

gnomAD: No allele frequency available, so no MAF to report.

PMID: 42428486

Gene: MYBPC3

HGNC: HGNC:7551

AdditionalInfo:Single-case report, no case numbering system used. Treated with dapagliflozin, metoprolol, rivaroxaban, and recombinant human BNP for 13 days, discharged on the first three; mexiletine added at 1-week follow-up for persistent palpitations. ICD recommended but declined due to financial constraints; 3-month follow-up showed good adherence with occasional palpitations and no serious arrhythmic events. Authors conclude MYBPC3 c.278delA is likely pathogenic for HCM, while the KCNJ5 variant shows no clinical phenotype in the proband or her son and may be incidental or a modifier.⁠

PMID: 27082122

Gene: TNNT2

HGNC ID: 11949

PMID: 34588271

Gene: MYBPC3

HGNC ID: HGNC:7551

PMID: 30009132

Gene: MYBPC3, multiple genes, cohort study

HGNC ID: HGNC:7551

PMID: 30896616

Gene: MYBPC3

HGNC ID: HGNC:7551

PMID: 31179125

Gene: TPM1

HGNC ID: 12010

PMID: 35861968

Gene: TNNT2

HGNC ID: HGNC:11949

33101033

MyBPC3

HGNCID:7551

Case1: Female, 23 years old, ethnicity not stated

DiseaseAssertion: Hypertrophic cardiomyopathy (HCM)

FamilyInfo: Mother, brother, and sister carry the same MYL2 mutation. Mother has phenotypic HCM without scar or high-risk features for sudden cardiac death. Sister and brother remain phenotypically negative with yearly imaging.

ParentalTesting: Maternal testing confirmed — mother carries the same MYL2 mutation and has phenotypic HCM. Paternal testing not reported.

CasePresentingHPOs: HP:0011675, HP:0001279, HP:0001962, HP:0004756

CaseHPOFreeText: During a sprinting drill, she developed a 42-second episode of polymorphic VT with spontaneous termination. The ambulatory rhythm monitoring showed a ~4% premature ventricular contraction (PVC) burden without sustained or nonsustained VT. CPET 2 demonstrated monomorphic nonsustained VT at peak exertion. Given exercise-induced polymorphic VT, she underwent placement of a subcutaneous implantable cardioverter-defibrillator (ICD) for secondary prevention. In the emergency department, high-sensitivity troponin rose from 105 to 303 ng/L. Cardiac magnetic resonance imaging (MRI) demonstrated normal LV function with subepicardial late gadolinium enhancement (LGE) in the basal to mid inferolateral wall, concerning for acute myocarditis

CaseNotHPOs:HP:0100749, HP:0002094, HP:0031972, HP:0001714

CaseNotHPOFreeText: Normal LV size and function on echocardiography. Normal strain. Repeat cardiac MRI showed complete resolution of LGE. Normal biventricular size, thickness, and function without LGE or scar on third MRI. No sustained VT/VF after ICD placement. Normal complete blood count and basic metabolic panel. Coronary CT angiography unremarkable.

CasePreviousTesting: She underwent coronary computed tomography angiography to rule out ischemia and anomalous coronary origins, which was unremarkable. Cardiac magnetic resonance imaging (MRI) demonstrated normal LV function with subepicardial late gadolinium enhancement (LGE) in the basal to mid inferolateral wall, concerning for acute myocarditis. Follow-up transthoracic echocardiography revealed normal LV size and function with normal strain, and repeat cardiac MRI showed complete resolution of LGE. She underwent maximal cardiopulmonary exercise testing (CPET), exercising for 13 minutes and 15 seconds, achieving 15 METs with a VO2 max of 40.4 mL/kg/min, which demonstrated frequent PVCs without nonsustained ventricular tachycardia (VT). Normal complete blood count and basic metabolic panel, aspartate aminotransferase, 38 U/L, alanine aminotransferase, 38 U/L, magnesium 2.2 mg/dL, thyroid-stimulating hormone, 1.96 μIU/mL, hemoglobin A1c, 5.8%.

Genotyping Method: Comprehensive genetic testing identified a pathogenic MYL2 variant.

FunctionalAnalysis: No functional analysis of the variant was performed

Variant: NM_000432.4:c.173G>A

ClinVar: 14067

CAID: CA009915

gnomAD: 12:111352091 C / T, chr12-110914287-C-T

AdditionalInfo: NR

PMID: 41999369

Gene: MYL2

HGNC ID: 7583

PMID: 31127036

Gene: MYL2

HGNC ID: 7583

Case1: Male, Infant, ethnicity not stated

DiseaseAssertion: congenital fiber-type disproportion (CFTD) and fatal infantile cardiomyopathy

FamilyInfo: The father was a healthy 20-yr old with no particular medical concerns, and there was no family history of neuromuscular or genetic disorders on either side. Both parents confirmed as heterozygous carriers of the MYL2 c.188del variant by Sanger sequencing

ParentalTesting: Both parents were confirmed as heterozygous carriers of MYL2 c.188del p.(Asn63Metfs7) by Sanger sequencing. Father confirmed as heterozygous carrier of NEB c.25435C>T p.(Gln8479)

CasePresentingHPOs: HP:0001290, HP:0001252, HP:0001640, HP:0001638, HP:0001639

CaseHPOFreeText: Newborn exam revealed normal first and second heart sound with gallop rhythm and palpable liver at the right costal margin, as well as generalized hypotonia and diminished reflexes. Echocardiogram was performed at 11 d of age and revealed patent foramen ovale with left to right shunt and right atrial enlargement. At age 5 mo, the proband was admitted to hospital in decompensated heart failure and intubated on inotropic support. Echocardiography revealed left ventricular dilatation, mild to moderate mitral valve regurgitation, and left atrial enlargement, with left ventricular function moderately to severely decreased with shortening fraction of 12% and ejection fraction of 23%. A vastus lateralis biopsy performed at 5 mo of age because of persistent muscle weakness and hypotonia revealed variability in fiber size with checkerboard pattern of 1:1 ratio of type 1 and type 2 fibers exhibiting hypotrophy of type 1 fiber size in comparison to the type 2 fibers. high lactate level (7.8 mmol/L)

CaseNotHPOs: NR

CaseNotHPOFreeText: Gomori trichrome–stained light micrographs and electron microscopy (EM) showed no evidence of ragged red fiber or nemaline rods, and oxidative stains revealed no evidence of cores, targetoid, or target fibers. Normal serum creatine kinase level. Normal birth weight, length, and head circumference. There was no histopathologic evidence of Pompe disease and GAA enzyme-level testing was normal. Genetic testing for POLG and Noonan syndrome genes normal

CasePreviousTesting: Genetic testing was performed for DNA polymerase γ, catalytic subunit (POLG) and Noonan syndrome genes (PTPN11, SOS1, KRAS, RAF1, BRAF, MAP2K1, MAP2K2, and HRAS), all of which were normal. There was no histopathologic evidence of Pompe disease and GAA enzyme-level testing was normal. Muscular dystrophy was considered unlikely given the histopathologic findings and normal serum creatine kinase level.

Genotyping Method: Next-generation sequencing was performed by the Laboratory for Molecular Medicine (LMM) of Partners Healthcare Personalized Medicine using the Agilent SureSelect Design process. The gene panel utilized an all exon approach for 43 genes of interest for neuromuscular and cardiac conditions by targeting coding exons with bait out to coding sequence (CDS) ±65 bases. The complete coding regions of all genes were sequenced to average depth of 316 reads

FunctionalAnalysis: No functional analysis of the variant was performed

Variant: NM_000432.3:c.188del

ClinVar: NR

CAID: UnregisteredVariant

gnomAD: NR

AdditionalInfo: This case also has a heterozygous pathogenic NEB variant c.25435C>T p.(Gln8479*) inherited from the father, classified as pathogenic but considered unlikely to be a significant contributor to disease as no second NEB allele was identified.

Case1: Male, Infant,

DiseaseAssertion: Dilated cardiomyopathy

FamilyInfo: Healthy, reportedly non-consanguineous, and had no known history of cardiomyopathy, heart failure, arrhythmia, sudden unexplained death, neuromuscular disease, or inherited metabolic disorder

ParentalTesting: Both parents were confirmed as heterozygous carriers by trio-based whole-exome sequencing.

CasePresentingHPOs: HP:0012378, HP:0030831, HP:0030864, HP:0033113, HP:0001712,

CaseHPOFreeText: “On arrival, he appeared pale, tachypneic, and fatigued, with subcostal retractions and scattered rhonchi and crepitations on chest auscultation. Cardiac examination revealed a gallop rhythm. Electrocardiography demonstrated biatrial enlargement, left ventricular hypertrophy, and borderline QT prolongation.”

CaseNotHPOs: NR

CaseNotHPOFreeText: No dysmorphic features recognized clinically, normal social interaction and visual tracking for age, normal brain MRI (normal cerebral structure and myelination, no malformation or demyelination), normal skeletal survey, creatine kinase within normal range, broad metabolic screening unrevealing, no pericardial effusion on echocardiography, no overt skeletal myopathy clinically recognized, negative SMA molecular testing, negative Prader–Willi syndrome methylation analysis

CasePreviousTesting: Broad metabolic screening was unrevealing. Creatine kinase was within the normal range. Molecular testing for spinal muscular atrophy and methylation analysis for Prader–Willi syndrome was negative. Brain magnetic resonance imaging performed at 9 months of age demonstrated normal cerebral structure and myelination, without malformation or evidence of demyelination. A skeletal survey was also normal. Additional investigations for muscular dystrophy and primary myopathic disorders had been initiated but were still incomplete at the time of his acute deterioration.

Genotyping Method: Trio-based whole-exome sequencing. Genomic DNA extracted from peripheral blood. Exome enrichment targeting coding exons and flanking splice junctions of >20,000 protein-coding genes. Illumina platform, mean on-target coverage >100×, ≥98% of targeted bases covered at ≥20× depth. Alignment to GRCh37/hg19, GATK-based variant calling pipeline.

FunctionalAnalysis: No functional analysis was performed.

Variant: NM_000432.4:c.413T>A

ClinVar: 840366

CAID: CA042802

gnomAD: 12:111348969 A / T, chr12-110911165-A-T

Case#: Female, 57, Korea

DiseaseAssertion:hypertrophic cardiomyopathy

FamilyInfo: Proband and 13 family members with diverse phenotypic expression of cardiomyopathies, elder sister had expired due to severe RCMP. large family, in which the p.Arg145Trp mutation of TNNI3 causes diverse phenotypes ranging from RCMP to HCMP to near-normal heart. Six relatives with RCMP or near-normal phenotypes also carried this mutation. Family pedigree (Figure 1) and Clinical data of affected individuals in a family with the c.433C>T mutation (table 1)

CasePresentingHPOs:HP:0002094, HP:0001640, HP:0001639, HP:6000313, HP:0031295, HP:0001670, HP:0004757, HP:0005135, HP:0004756, HP:0001962

CaseHPOFreeText:restrictive filling pattern, delayed hyper-enhancement, which reflects fibrotic change in the myocardium in the hypertrophied segments (Fig. 2D).

CaseNotHPOs:HP:0032092

CaseNotHPOFreeText:normal LV systolic function and normal cavity size

CasePreviousTesting:Chromatograms, Echocardiogram

Genotyping Method:Sanger Sequencing (Fig. 5)

FunctionalAnalysis:heterozygous nonsynonymous mutation

Variant:NM_000363.5(TNNI3):c.433C>T (p.Arg145Trp)

CAID:CA021667

gnomAD:chr19-55154146-G-A

PMID:28382084

Gene:TNNI3

HGNC ID:11947

PMID: 37646638

Gene: TNNI3

HGNC ID: 11947

PMID:22957257

Gene:MYL3

HGNC ID:7582

Case2: A 49 year old woman

DiseaseAssertion: Carried a novel MYBPC3 T494I mutation

FamilyInfo: Both parents were older than 80 years, had no cardiovascular symptoms and declined participation in the study

ParentalTesting:NR

CasePresentingHPOs: HP:0034307, HP:0012666, HP:6000091

CaseHPOFreeText: Had onset of symptoms a few days after giving birth to her first child. She had a short, aggressive disease period, which resulted in HTX within 3 months of onset. Age 35 at onset. Has left ventricular end-diastolic diameter (in mm and indexed by body surface area (cm/m2)) 62 mm and 3.2 cm/m2. A left ventricular ejection fraction of 20%. An ECG at normal. New York Heart Association (NYHA) as 4, Clinical status as heart transplantation (HTX), CAG as normal. HTX, 36 years, postpartum.

CaseNotHPOs:HP:0011675

CaseNotHPOFreeText:No Arrhythmia.

CasePreviousTesting:NR

Genotyping Method:genetically screened, also using GenBank with PCR by amplifying the coding region.

FunctionalAnalysis:NR

Variant:NM_000256.3:c.1481C>T

ClinVar:NR

CAID:CA380325267

gnomAD:NR

AdditionalInfo:This index case carried a novel MYBPC3 T494I mutation, which replaces a conserved hydrophilic side chain with a branched neutral side chain in domain C3 of cardiac myosin-binding protein C (cMyBPC); such an alteration may interfere with the secondary structure of the C3 domain. The missense mutations G490R, R495Q and R502W, all located in the proximity of the 494 residue, have all been described as associated with HCM.

PMID: 19293840

Gene: MYH7

HGNC ID: 7577

PMID: 19087273

Gene: TNNT2

HGNC ID: 11849

Case#:24-year-old male

DiseaseAssertion:non-obstructive HCM and long QTc

FamilyInfo:family history of long QT (mother and maternal grandmother), (family pedigree in Fig. 2)

ParentalTesting:Sanger sequencing done in the father confirming the paternal origin of the variant.

CasePresentingHPOs:HP:0001712, HP:0001657, HP:0005135

CaseNotHPOs:HP:0001654, HP:0006673

CasePreviousTesting: Cardiac MRI, Electrocardiogram, echocardiogram

Genotyping Method:Next Generation Sequencing

FunctionalAnalysis:Pathogenic missense variant

Variant:NM_000363.5(TNNI3):c.592C>G (p.Leu198Val)

ClinVar:177694

CAID:CA022019

gnomAD:chr19-55151875-G-C

PMID:33777698

Gene:TNNI3

HGNC ID:11947

PMID:38548731

Gene:TNNI3

HGNC ID:11947

Case#:14 year old Female

DiseaseAssertion:nonobstructive hypertrophic cardiomyopathy

FamilyInfo:lacked any family history of cardiomyopathy, including sudden death or cardiac hypertrophy, Family Pedigree (Figure. 1a)

ParentalTesting:none, healthy parents

CasePresentingHPOs:HP:0001663

CaseHPOFreeText: cardiopulmonary arrest

CaseNotHPOs: HP:4000004

CaseNotHPOFreeText: myocardial edema, ventricular arrhythmias, obstructed outflow tract

CasePreviousTesting: echocardiogram, cardiac MRI

Genotyping Method:Whole genome sequencing

FunctionalAnalysis:heterozygous missense variant

Variant: NM_000363.5:c.583A>T (p.Ile195Phe)

CAID:CA407439576

PMID:30953456

Gene:TNNI3

HGNC ID:11947

Case#:52 year old female from a small mountainous village in Peloponnese, Greece

DiseaseAssertion:severely manifested phenotype of RCM leading to heart transplant at 41

FamilyInfo:Family Pedigree Figure 1.Parents were third-degree cousins from the same village and were heterozygous for the same variant but displayed no symptoms of the disease. The older sister who was also found heterozygous was asymptomatic. Twin sister and brother were homozygous for the same variant and displayed a restrictive and a hypertrophic phenotype, respectively. Their children are all carriers of the mutation and remain asymptomatic until the age of 21

ParentalTesting:Family of the proband had Electrocardiogram and Doppler Echocardiogram (shown in figure 2) as well as TNNI3 genetic testing by targeted Sanger sequencing for the detection of the variant. Her twin sister and her brother were found homozygous for the variant, while both parents and the older sister were found heterozygous.

CasePresentingHPOs:HP:0002875, HP:0004757

CaseNotHPOFreeText:normal left ventricular dimensions

CasePreviousTesting:electrocardiogram, Right heart catheterization

Genotyping Method:NGS (filtered using VariantStudio Data Analysis Software and the Sophia Genetics DDM platform)

FunctionalAnalysis: a novel homozygous TNNI3 variant

Variant:NM_000363.4:c.586G > C, p.(Asp196His)

ClinVar:2169619

CAID:CA407439559