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.