Coexistence of Genetic Diseases Is a New Clinical Challenge: Three Unrelated Cases of Dual Diagnosis

The third patient was a 27-year-old man who was the son of third-degree consanguineous parents.

A 25-year-old White man presented with bilateral central vision loss due to foveal lesions consisting of vitelliform fluid.

RP-087M30c.6397T>Cp.C2133RD1D2D322.80Y

STGD in 48 patients (55%) was explained by recessive ABCA4 mutations (supplemental table S2). Only 22 patients could be solved using previously known STGD causing mutations. However, we identified 35 novel mutations in ABCA4 contributing to the diagnosis of 25 STGD patients. This contained 10 novel mutations leading to amino acid substitutions already known to cause disease and mutations known to cause diseases other than STGD. In addition, we identified 13 novel nonsense mutations. The remaining 12 novel mutations are well justified, and novel mutations were either completely absent or extremely rare in controls.

Comprehensive analysis of Stargardt macular dystrophy patients reveals new genotype-phenotype correlations and unexpected diagnostic revisions

STGD in 48 patients (55%) was explained by recessive ABCA4 mutations (supplemental table S2). Only 22 patients could be solved using previously known STGD causing mutations. However, we identified 35 novel mutations in ABCA4 contributing to the diagnosis of 25 STGD patients. This contained 10 novel mutations leading to amino acid substitutions already known to cause disease and mutations known to cause diseases other than STGD. In addition, we identified 13 novel nonsense mutations. The remaining 12 novel mutations are well justified, and novel mutations were either completely absent or extremely rare in controls.

Bilateral visual loss, behavioral changes, and overlooking in a young child with stargardt disease: Neurodiagnostic considerations

Bilateral visual loss, behavioral changes, and overlooking in a young child with stargardt disease: Neurodiagnostic considerations

Patient 1 (P1) experienced reduced vision from age 5 and was referred to ophthalmology testing at Haukeland University Hospital at age 12.

Patient 2 (P2)

At least 1 disease-causing ABCA4 variant was identified in 38 patients (90%), including 13 novel variants; ≥2 variants were identified in 34 patients (81%). Patients with childhood-onset STGD more frequently harbored 2 deleterious variants (18% vs 5%) compared with patients with adult-onset STGD.

Clinical and molecular characteristics of childhood-onset Stargardt disease

Screening of ABCA4 Gene in a Chinese Cohort With Stargardt Disease or Cone-Rod Dystrophy With a Report on 85 Novel Mutations

Eighty-four unrelated STGD1 patients were found to carry two or more disease-causing ABCA4 mutations, and cosegregation analyses were performed in 54 (64.3%). (See Supplementary Table S3 for a summary of clinical phenotype of STGD1 patients). The mean disease onset age of the patients was 13.1 years (range, 2–44 years), and half of these patients experienced their symptoms of visual impairment in their first decade. We classified the patients into three groups by their disease onset age. For the patients in the first group, whose disease onset ages were between 1 and 10 years, the fraction (45.3%, 19/42) of patients carrying compound heterozygous or homozygous deleterious mutations (nonsense, frameshift insertion or deletion, or splicing mutations) or complex alleles was much higher than those observed for the patients in the group 2 (24.1%, 7/29) and group 3 (15.4%, 2/13), whose disease onset ages were from 11 to 20 years or older than 20 years, respectively. In contrast, the percentage of patients carrying compound heterozygous or homozygous missense mutations was higher in group 3 than in group 1 or group 2 (Table 2). The most common mutation (p.Y808X) was detected in 12 patients, and all were heterozygous compound with missense (6 patients), splicing (1 patient), and insertion or deletion (5 patients) mutations. The two most frequent missense mutations (p.F2188S and p.N965S) were identified as heterozygous. In 84 patients, 9 patients carried complex mutations, and 4 of those 9 patients carried a common complex allele p.E328V/p.E1036K. All these patients had early onset age and relatively severe visual acuity defects. One patient (010222) also carried three heterozygous mutations (p.E328, p.E1036K, and p.R1843W); however, he did not harbor the common complex allele p.E328V/p.E1036K, as only p.E1036K was detected in his son in the subsequent cosegregation analysis. Compared to the four patients carrying the common complex alleles (p.E328V/p.E1036K), patient 010221 had a late onset age (44 years old).  Table 2 View Table Correlations Between Onset Age of STGD Patients and Their Carrying Mutations

Retinal findings in a patient with mutations in ABCC6 and ABCA4

ABCA4-retinopathy

V1 H1 Exon 36.1–3 G>A chr1:94,484,001 c.5196+1137G>A 4 4 0

V1 H1 Exon 36.1–3 G>A chr1:94,484,001 c.5196+1137G>A 4 4 0 0

V1 H1 Exon 36.1–3 G>A chr1:94,484,001 c.5196+1137G>A 4 4 0 0

V1 H1 Exon 36.1–3 G>A chr1:94,484,001 c.5196+1137G>A 4 4 0 0

V1 H1 Exon 36.1–3 G>A chr1:94,484,001 c.5196+1137G>A 4 4 0 0

Carrier frequency analysis of mutations causing autosomal-recessive-inherited retinal diseases in the Israeli population

MD-0242ABCA412c.1715G>Cp.Arg572ProNot detected18YesABCR400

MD-0302 ABCA4 12 c.1622T>C p.Leu541Pro 42 c.5882G>A p.Gly1961Glu 17 Yes ABCR400

MD-0467 ABCA4 12 c.1622T>C p.Leu541Pro 43 c.5917delG p.Val1973* 7 NP ABCR400

Inherited retinal diseases (IRDs) comprise a phenotypically and genetically heterogeneous group of ocular disorders that cause visual loss via progressive retinal degeneration. Here, we report the genetic characterization of 1210 IRD pedigrees enrolled through the Japan Eye Genetic Consortium and analyzed by whole exome sequencing. The most common phenotype was retinitis pigmentosa (RP, 43%), followed by macular dystrophy/cone- or cone-rod dystrophy (MD/CORD, 13%). In total, 67 causal genes were identified in 37% (448/1210) of the pedigrees. The first and second most frequently mutated genes were EYS and RP1, associated primarily with autosomal recessive (ar) RP, and RP and arMD/CORD, respectively. Examinations of variant frequency in total and by phenotype showed high accountability of a frequent EYS missense variant (c.2528G>A). In addition to the two known EYS founder mutations (c.4957dupA and c.8805C>G) of arRP, we observed a frequent RP1 variant (c.5797C>T) in patients with arMD/CORD.

We identified 44 novel sequence changes (Table 3). Of these changes, 30 were potentially pathogenic and 14were classified as potentially neutral polymorphisms or changes of unknown significance.

15 MEH c.5196+1137G>A p.[=,M1733Efs∗78] c.[1715G>A;2588G>C] p.[(R572Q;G863A,G863del] Y U 20546

Clinical and Genetic Spectrum of Stargardt Disease in Argentinean Patients

c.1A>G, p.Met1Val

Supplementary data. bjophthalmol-2018-312064supp004.pdf

Supplementary data. bjophthalmol-2018-312064supp004.pdf

Unusual clinical phenotype of Stargardt disease

Unusual clinical phenotype of Stargardt disease

able S9. List of unique causative variants detected in 858 STGD probands mmc8.xlsx (19.3KB, xlsx) Table S11. STGD1 cases with at least two (likely) causal ABCA4 variants

Targeted sequencing and in vitro splice assays shed light on ABCA4-associated retinopathies missing heritability

Table S9. List of unique causative variants detected in 858 STGD probands mmc8.xlsx (19.3KB, xlsx) Table S11. STGD1 cases with at least two (likely) causal ABCA4 variants mmc9.xlsx (39.6KB, xlsx)

Next-generation genetic testing for retinitis pigmentosa

29-year-old man

Finally, we examined whether the phenotype‐associated known/candidate pathogenic variants could explain the patient's disease, andif the MAF in population‐matched control data (8.3kJPN) was relatedto disease prevalence. Patients were classified as “Solved” if theirgenotype was consistent with their clinical phenotype. Patients wereclassified as “Partially solved” when a heterozygous known/candidatepathogenic variant was detected in a recessive allele, but without anadditional variant in trans. Patients were categorized as “Unsolved” iftheir genotypes exhibited either no candidate pathogenic variants ormultiple heterozygous pathogenic variants that did not explain thephenotype clearly. Variants annotated as causal for solved patients arelisted in Supporting Information: Table S2. Novel variants identified inthis study are listed in the second sheet of Table S2. SupportingInformation: Table S3 shows the phenotypes and genotypes of solvedpatients.2.4 | Statistical analysisBefore counting the allele frequency in our cohort, the list ofpatients was modified to contain only the proband to avoid theoverrepresentation of pedigrees with larger numbers of affectedindividuals. Inter‐pedigree comparisons of genetic diagnoses evaluat-ing proband only and proband with family members were performedby the chi‐square test. Enrichments of the pathogenic variants ingenetically solved and unsolved patients were compared by the one‐sided binominal test. Allele frequencies were compared with thehighest allele frequencies among the 8.3KJPN, HGVD, ExAC_EAS, andgnomAD_EAS databases. Statistical analyses were performed byR (ver. 4.0.3).2.5 | Detection of RP1:c.4052‐4053ins328(Alu insertion)Previously reported primers were used to amplify the expectedAlu‐inserted region (Nikopoulos et al., 2019). Genomic DNA wasamplified with Prime Star (TAKARA) following the manufacturer'sSUGA ET AL . | 310981004, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/humu.24492 by Mie University, Wiley Online Library on [07/11/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

Finally, we examined whether the phenotype‐associated known/candidate pathogenic variants could explain the patient's disease, andif the MAF in population‐matched control data (8.3kJPN) was relatedto disease prevalence. Patients were classified as “Solved” if theirgenotype was consistent with their clinical phenotype. Patients wereclassified as “Partially solved” when a heterozygous known/candidatepathogenic variant was detected in a recessive allele, but without anadditional variant in trans. Patients were categorized as “Unsolved” iftheir genotypes exhibited either no candidate pathogenic variants ormultiple heterozygous pathogenic variants that did not explain thephenotype clearly. Variants annotated as causal for solved patients arelisted in Supporting Information: Table S2. Novel variants identified inthis study are listed in the second sheet of Table S2. SupportingInformation: Table S3 shows the phenotypes and genotypes of solvedpatients.

In contrast, we found that the expression levels of the WT and all three mutant proteins were equivalent as determined by western blotting (Fig. 3B).

We identified 255 patients (87.9 %) harboring biallelic ABCA4 variants, 27 probands (9.3 %) with two or three variants but lacking familial segregation analysis, and eight patients (2.8 %) with monoallelic ABCA4 variants (Supplemental Table S4). We detected 268 distinct ABCA4 variants, consisting of 114 missense, 35 nonsense, 34 frameshift deletion or insertion, 31 canonical splice variants, 13 noncanonical splice site variants, 9 in-frame deletion or insertion, 9 DIVs, 4 structural variations, and 19 complex variants (Fig. 2).

We identified 255 patients (87.9 %) harboring biallelic ABCA4 variants, 27 probands (9.3 %) with two or three variants but lacking familial segregation analysis, and eight patients (2.8 %) with monoallelic ABCA4 variants (Supplemental Table S4). We detected 268 distinct ABCA4 variants, consisting of 114 missense, 35 nonsense, 34 frameshift deletion or insertion, 31 canonical splice variants, 13 noncanonical splice site variants, 9 in-frame deletion or insertion, 9 DIVs, 4 structural variations, and 19 complex variants (Fig. 2).

Mutation Spectrum of the ABCA4 Gene in 335 Stargardt Disease Patients From a Multicenter German Cohort—Impact of Selected Deep Intronic Variants and Common SNPs

We found statistically significant association for six variations (c.1268A>G, c.4203C>A, c.5603A>T, c.5682G>C, c.5843C>T, c.6249C>T) (FDR < 0.05, Supplementary Table S4)

Stargardt disease (STGD) and fundus flavimaculatus are infrequent autosomal recessive conditions characterized by a juvenile macular dystrophy and variable degrees of peripheral retinal changes. Linkage analysis performed in 47 STGD/fundus flavimaculatus families demonstrated significant linkage to 13 polymorphic DNA markers on chromosome 1p. The maximum combined two-point lod score was 32.7 (maximum recombination fraction [phi max] = .006) with the polymorphic marker D1S188. Our data demonstrate that STGD and fundus flavimaculatus are the same disorder clinically and genetically and provide further evidence for genetic homogeneity of this phenotype. Analysis of recombination events on disease chromosomes placed the STGD gene within a 4-cM interval between markers D1S435 and D1S236. A physical map was constructed of a YAC contig flanking STGD, from markers D1S500 to D1S495, and includes the critical interval delineated by historical recombinants. This contig spans approximately 31 cM, with one gap (3-5 cM) that is outside the 4-cM critical region. Localization of STGD to a single YAC contig will facilitate its positional cloning.

A YAC contig encompassing the recessive Stargardt disease gene (STGD) on chromosome 1p

Representation of Women Among Individuals With Mild Variants in ABCA4-Associated Retinopathy: A Meta-Analysis

Sixty-six individuals representing 54 families were studied (Supplementary Material, Table S1). All individuals were found to harbor two ABCA4 variants likely to cause the retinal disease (18,20–26). In 40 families (74%), independent segregation of the two alleles was demonstrated. The ages at the time of their first visit ranged from 9 to 74 years (mean = 35.9, median = 35.2 years); in the majority of individuals (36/66=55%), data were available from a second visit that occurred on average 8.7 years (range=2–20 years, median = 6.9 years) after the first visit.

ABCA4 disease progression and a proposed strategy for gene therapy

Introducing a comprehensive genetic testing strategy by combining single gene Sanger sequencing, next-generation sequencing (NGS) including whole exome sequencing (WES), and a specific hereditary eye disease enrichment panel (HEDEP) sequencing, to identify the disease-causing variants of 800 Chinese probands affected with non-syndromic IRDs.

Detailed analysis of an enriched deep intronic ABCA4 variant in Irish Stargardt disease patients

Pt-75Mc.4539 + 2028C > Tp.[= ,Arg1514Leufs*36]c.2453G > Ap.(Gly818Glu)

A 19-year-old female

Superotemporal predisposition to traumatic subretinal fibrosis in Stargardt disease: A case report

Mutations of the retinal specific ATP binding transporter gene (ABCR) in a single family segregating both autosomal recessive retinitis pigmentosa RP19 and Stargardt disease: evidence of clinical heterogeneity at this locus

Mutations of the retinal specific ATP binding transporter gene (ABCR) in a single family segregating both autosomal recessive retinitis pigmentosa RP19 and Stargardt disease: evidence of clinical heterogeneity at this locus

Exome Sequencing of Index Patients with Retinal Dystrophies as a Tool for Molecular Diagnosis

This work reported presence of 22 alterations, including two changes not found in other populations, c.2T>C (p.Met1Thr) and c.4036_4037delAC (p.Thr1346fs), and two novel disease associated variants, c.400C>T (p.Gln134X) and c.4720G>T (p.Glu1574X).

Retinal Phenotypes in Patients Homozygous for the G1961E Mutation in the ABCA4 Gene

The proband of Family #1 (Patient #1, II:1 in pedigree Figure 1A)

son (the proband of Family #3, pedigree in Figure 1C)

CLINICAL CHARACTERIZATION OF STARGARDT DISEASEPATIENTS WITH THE p.N1868I ABCA4 MUTATION

Quantitative Fundus Autofluorescence and Genetic Associations in Macular, Cone, and Cone-Rod Dystrophies

A novel statistical method for interpreting the pathogenicity of rare variants

Screening of reported pathogenic variants in ABCA4 for Stargardt (STGD) The disease prevalence of STGD is estimated as 1 in 10000 individuals4. It has been estimated that about 70% of STGD patients carry variants in ABCA45. Therefore, this represents the scenario of a recessive disease with a relatively homogeneous genetic cause. We screened 945 reported pathogenic variants in ABCA4 genes collected in HGMD. Among them, 11 variants are likely benign, as their population AF in is higher than 0.7% (1/20000‾‾‾‾‾‾‾‾√)<math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="M11"><mrow><mrow><mo>(</mo><mrow><msqrt><mrow><mn>1</mn><mo>/</mo><mn>20000</mn></mrow></msqrt></mrow><mo>)</mo></mrow></mrow></math>, the cutoff based on STGD disease prevalence, therefore were excluded from further analysis. The remaining 934 variants were subjected to our test model. As a result, 26 variants with the AF in the range of 0.46% to 0.03% were identified as likely benign (Binomial test1, Bonferroni correction p-value ≤ 0.05/934 and test2 Bonferroni correction p-value > 0.05/934) (Figure 3A).

Impact of Next Generation Sequencing in Unraveling the Genetics of 1036 Spanish Families With Inherited Macular Dystrophies

Supplement 3iovs-63-2-11_s003.pdf (1.1M)GUID: 00045B54-7E12-4EE1-B50D-27CAC38DD633

ilename Description aos14218-sup-0001-TableS1.xlsxMS Excel, 27.1 KB Table S1. List of genetic variants found in IRD patients, Norway, 2018. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Inherited retinal disease in Norway – a characterization of current clinical and genetic knowledge

Next, we measured the effect of disease-associated mutations on the ATPase activity of ABCA4. WT and ABCA4 variants were solubilized in CHAPS, purified by immunoaffinity chromatography, and subsequently reconstituted into PE-containing liposomes at similar protein concentrations. The ATPase activity of the mutants in the presence and absence of N-Ret-PE substrate is shown in Figure 6A, ​A,6B.6B. As previously reported,25,47 addition of 40 μM all-trans retinal to WT ABCA4 resulted in a 1.8- to 2.5-fold increase in ATPase activity (Fig. 6). The ATPase activity of the mutants was measured at the same protein concentration as WT ABCA4 to determine the effect of the mutation on the functional activity of ABCA4. Five mutants (p.Val552Ile, p.Ala1038Val, p.Ala1357Thr, p.Ala1794Pro, and p.Leu2027Phe) showed reduced basal ATPase activity relative to WT ABCA4 (∼40%–85%), but this activity was stimulated 1.6- to 3.0-fold by the addition of all-trans retinal. On the other hand, p.Gly72Arg, p.Met448Lys, p.Leu541Pro, p.Gly1091Glu, p.Gly1961Glu, and p.Arg2077Trp variants showed drastically reduced basal activity with little or no substrate stimulation.Open in a separate windowFigure 6ATPase activity of ABCA4 variants. The ATPase activity of immunopurified and reconstituted ABCA4 variants was measured in the presence or absence of all-trans retinal. (A) Quantification of the basal and retinal-stimulated ATPase activity of ABCA4 variants normalized to WT basal ATPase activity. ATPase assays were carried out using similar concentrations of purified ABCA4. Data expressed as an average ± SD for n ≥ 3 independent experiments. (B) Representative curves of specific ATPase activity as a function of all-trans retinal concentration for WT and ABCA4 variants. (C) Relative basal ATPase activity of WT and A1794P using equal amounts of transfected HEK293T cells. Data expressed as an average ± SD. Measurements were done in triplicate.To more directly evaluate the expression and function of the p.Ala1794Pro variant, we transfected HEK293T cells separately with WT ABCA4 and the p.Ala1794Pro mutant cDNAs at similar levels. After solubilization in CHAPS buffer, the samples were subjected to high-speed centrifugation and the supernatant was reconstituted into liposomes for analysis of its basal and substrate activated ATPase activity. As shown in Figure 6C, the p.Ala1794Pro had a significantly reduced activity due largely to the low expression of this variant. These studies indicate that only a small fraction of the p.Ala1794Pro mutant folds into a functionally active protein and correlates well with the phenotype of patient 5.

Correlating the Expression and Functional Activity of ABCA4 Disease Variants With the Phenotype of Patients With Stargardt Disease

Variants S206R and L541P have reduced basal ATPase and S206R shows little, and L541P shows no, stimulation by retinal (Fig. 4a).

Figure 3: Protein yield and ATP-binding capacity of 37 naturally occurring ABCR variants produced in transiently transfected 293 cells.Membranes were analysed by immunoblotting with affinity-purified anti-ABCR antibodies (top) and photoaffinity labelling with α-32P azido-ATP (bottom). We loaded 1 μg (immunoblotting) or 2.5 μg (azido-ATP labelling) of total membrane protein, as determined by Bradford assay, per track. The mutations that reside in NBD-1 and NBD-2 are indicated above the corresponding lanes. The relative levels of the different variant proteins and the extent of azido-ATP labelling were observed to be highly reproducible in multiple independent experiments. ABCR (large arrowhead); an endogenous 55-kD protein (small arrowhead) serves as an internal control for azido-ATP labelling. Molecular mass standards are shown on the left in kD.

Patient 4, a 33-year-old Caucasian woman, presented in July 1998 with a gradual decline in visual acuity over the last 9 years and a best-corrected visual acuity of 20/300 in both eyes.

STGD87 2588G→C Q1750X Yes

STGD47/164 IVS13+1G→A 2588G→C Yes

A total of 42 unrelated patients (28 men and 14 women) were included in this study. Two patients (A002 and A035) were from consanguineous families (Figure 1). The detailed clinical findings are presented in Data S1.

11 M 53 c.5461–10T>C ND

14 F 42 c.4222T >C c.4918C>T

Mutations in ABCA4 result in accumulation of lipofuscin before slowing of the retinoid cycle: a reappraisal of the human disease sequence

The locations of ABCA4 homozygous and hypomorphic missense mutations characterized in the present study are shown in Fig 1. These mutations are distributed throughout ABCA4 with 4 in ECD1 (p.Asn96Asp, p.Asn96His, p.Arg212Cys, p.Arg602Trp), 4 in ECD2 (p.Leu1430Pro, p.Gly1439Asp, p.Pro1486Leu, p.Ala1598Asp), 6 within or close to NBD1 (p.Gly863Ala, p.Asn965Ser, p.Thr1019Met, p.Glu1087Lys, p.Arg1108Cys, p.Arg1129Leu), and 6 within NBD2 (p.Leu1940Pro, p.Gly1977Ser, p.Leu2027Phe, p.Arg2030Gln, p.Arg2107His, p.Cys2137Tyr). The p.Asn1868Ile mutation is present in a loop connecting the V-shaped α-helical hairpin with membrane spanning segment 12 (TM12). Several mutations occur in well-defined motifs crucial for the binding and hydrolysis of ATP. The p.Asn965Ser and p.Glu1087Lys mutations occur in the Walker A (Gly-His-Asn-Gly-Ala-Gly-Lys-Thr) and Walker B (Val-Ile-Leu-Asp-Glu) motifs of NBD1, respectively, and the p.Gly1977Ser mutation is present in the Walker A (Gly-Val-Asn-Gly-Ala-Gly-Lys-Thr) motif of NBD2. The p.Arg2030Gln variant reported to display a mild disease phenotype in compound heterozygous STGD1 patients has been included in our analysis although this variant has yet to be found in a homozygous state.

STARGARDT DISEASE : Beyond Flecks and Atrophy

Patients older than 60 years or with ocular comorbidities such as diabetic retinopathy, uveitis, or glaucoma were excluded. From the remaining list, subjects for whom high-resolution SD-OCT imaging was available were selected. A review of the patient imaging and medical records was performed to identify those who received a clinical diagnosis of Stargardt macular dystrophy based on their clinical phenotype, including color fundus, infrared, FAF, and fluorescein angiography images and electroretinographic findings. 12

The proband

Phenotype–genotype correlations in a pseudodominant Stargardt disease pedigree due to a novel ABCA4 deletion–insertion variant causing a splicing defect

616; 41c.2453G>A; c.5824G>Cp. G818E (D); p. E1942Q (B;N)46c.6384A>Gp.H2128R (D)Compound heterozygous

ABCA4 mutational spectrum in Mexican patients with Stargardt disease: Identification of 12 novel mutations and evidence of a founder effect for the common p.A1773V mutation

1545c.6221G>Tp.G2074V (D; N)16c.2453G>Ap.G818E (D)Compound heterozygous

MD-1001 STGD1 44 c.6089G>A p.(Arg2030Gln) 47 c.6410G>A p.(Cys2137Tyr) - - - - - - - This study

MD-0247 STGD1 23 c.3386G>T p.(Arg1129Leu) 47 c.6410G>A p.(Cys2137Tyr) Yes 12 12 - 22y Cone-pattern 0.05/0.1 Riveiro-Alvarez et al.,2013

47 c.6410G>A p.(Cys2137Tyr) Aguirre-Lamban (2008) Hum Genet 123 547 8 missens

MD-0723 STGD1 23 c.3386G>T p.(Arg1129Leu) 47 c.6410G>A p.(Cys2137Tyr) - 13 13 Yes 15y Cone-pattern 0.2/0.2 This study

Intersection of Stargardt Dystrophy and AIDS: A Case Report

Patients and Methods The protocol of the study adhered to the provisions of the Declaration of Helsinki. After informed consent was obtained, blood samples were taken and molecular analysis on the ABCA4 gene was performed as described by Maugeri et al. 14 The charts of patients with ABCA4 mutations who originally had received diagnoses of isolated or autosomal recessive CRD were reviewed. All patients originated from the University Medical Centre Nijmegen (Nijmegen, The Netherlands) and the University of Heidelberg (Heidelberg, Germany). In this study the diagnosis of CRD was based on the following criteria: initial symptoms of blurred central vision without a history of night blindness, impairment of color vision, and fundoscopic evidence of maculopathy without or with mild peripheral retinopathy. 3 4 5 7 8 In patients with recordable ERGs a cone–rod pattern of degeneration had to be present (i.e., the photopic b-wave impairment had to be greater than or equal to the scotopic b-wave amplitude impairment). Patients 9250 and 13163, who had nonrecordable ERGs, were included because their histories and clinical features were similar to those of other patients with cone–rod degeneration and they were believed to represent advanced cases of CRD. In addition to an ophthalmic examination, Goldmann kinetic perimetry routinely was performed using III-4-e and I-4-e isopters. Color vision was tested with the Ishihara and Panel D15 tests, except in patients 9369, 9378, and 10125, who were tested under conditions described earlier. 18 Because these patients were examined in two different clinics and ERGs were recorded over a long period, the methods, instrumentation, and analysis techniques of the electroretinography varied. The ERGs in patients 9369, 9378, 10125, and 11872 were performed as described by Thijssen et al. 19 The ERG method used in patients 9370, 9553, 9633, and 13163 was described by Alexandridis and Krastel. 20 The ERGs of the remaining patients (9250, 9371, and 9650) are of a more recent date and were performed according to International Society for Clinical Electrophysiology of Vision (ISCEV) standards. 21 Fundus photographs were taken in most patients and some of the patients (9650, 9369, 9378, and 10125) also underwent fluorescein angiography.  Results The characteristics of 12 patients with ABCA4-associated retinal dystrophy resembling CRD are summarized in Table 1 . Most did not have affected family members, and therefore their retinal dystrophies could not be classified as autosomal dominant, autosomal recessive or X-linked. Four patients reported a brother or sister with subnormal vision. In view of the reputedly normal visual acuity of the parents and the molecular defects, the inheritance pattern of the gene defects in these patients (individuals 9303, 9369, 9553, and 13163) was classified as autosomal recessive.  The visual acuity of the patients did not exceed 20/200 and, on average, was much lower. With the exception of patient 9553, the age of onset was at or before the age of 12, and in each of the patients, blurred vision was the initial symptom. Night blindness did not occur except in patients 9378 and 10125, in the final stages of retinal degeneration. Evidence of maculopathy in the form of bull’s eye maculopathy or pigmentary changes was present in all the patients reported in this study (Fig. 1A) . The functional equivalent of the mainly centrally located retinal disease was a central scotoma, varying from 8° to more than 40°. In all but one patient, the scotoma was absolute. Only in patient 9378 was the central scotoma relative and surrounded by absolute scotomas. Fundoscopic evidence of early peripheral involvement of the retina was mild, and only in the later stages of the disease did peripheral changes characteristic of RP, such as narrowing of retinal vessels and bone spicula, occur in patients 9369 (Fig. 1B) and 10125. Similarly, mild constriction of the visual fields occurred only in two patients (9650 and 10125) and only in the advanced state. Color vision was tested in 10 patients. Six demonstrated a red–green defect, and in two of these (patients 11872 and 10125), it was accompanied by a blue-yellow defect. In the remaining four patients, color vision was so severely disturbed that the exact type of impairment could not be assessed.  The ERG recordings demonstrated degeneration of both rods and cones. When ERG responses could be elicited, the cones appeared to be affected as much as the rod photoreceptors and, in most of the patients, even more severely. The ERG responses in five patients progressively deteriorated until no photopic and scotopic responses could be recorded. In these patients, with exception of patients 9250 and 13163, ERG recordings of an earlier date were used in Table 1 . This applies to patient 9369, in whom an ERG was recorded at age 12 (all ERG responses had been nondetectable since the age of 21), patient 9378 at age 33 (all ERG responses at age 46 were nondetectable), and patient 10125 at age 8 (in 1998, at age 28, the ERG responses were no longer detectable). Recent ERG findings were not available for patients 9650 and 9371. Their ERGs were recorded in 1989 and 1985, respectively. The remaining ERG data were derived from ERG recordings performed in the past 4 years. Of patient 9371 only the ERG data in the left eye were available.  Two patients warrant a more detailed description, due to the unusual course of their retinal dystrophies. Patient 9378, at the age of 12, had blurred vision with fundoscopic evidence of irregular chorioretinal atrophy in the posterior pole. At that time, there were no peripheral abnormalities on ophthalmoscopy, and there was no history of night blindness. The ERG demonstrated an equal reduction of both cone- and rod-mediated responses. Later in life, however, fundoscopic changes developed that were characteristic of RP, and the patient reported a decrease in night vision. With fluorescein angiography partly confluent patches of chorioretinal atrophy were visible (Fig. 1C) .  The clinical picture of patient 10125 differed from that of the other patients, despite the mutation in the ABCA4 gene. Initially, disease in this patient was diagnosed as STGD because of the bull’s eye maculopathy, the granular pigment alterations in the macular area, and the pisciform flecks surrounding the posterior pole. At age 8 his visual acuity had decreased to 20/200 in both eyes. When he was referred to our clinic in 1998 at the age of 28, peripheral degeneration in the form of narrow retinal vessels and deposition of peripheral bone spicula had developed, in addition to the earlier described disease of the central retina. A fluorescein angiogram showed typical findings: a central small hypofluorescent spot enclosed by an ellipsoid—a markedly hyperfluorescent area that in turn was surrounded by hyperfluorescent dots against a dark background, most likely caused by obscuration of choroidal background fluorescence (Fig. 1D) . Early ERG recordings were not available, and the ERG tracings recorded at age 28 represent the final stage of the degenerative process, with absence of both cone and rod responses. This retinal dystrophy seemed to have evolved from STGD into more widespread retinal degeneration, resulting in loss of function of both rods and cones.  Discussion Progressive CRD is a clinically heterogeneous retinal disorder, but typical findings include reduced visual acuity, impairment of the central visual field, color vision deficits, and fundoscopic evidence of maculopathy, with no or few midperipheral retinal pigment deposits. 3 4 7 8 There is some dispute about typical ERG findings in CRD. Some state that the diagnosis of CRD must be based on the reduction or absence of cone responses in the presence of quantitatively less reduction in rod responses, whereas others state that an equal impairment of both photoreceptor systems, if accompanied by the characteristic features, suffices to justify the diagnosis of CRD. 3 7 8 22 Several propositions have been made in the past to classify cone–rod disorders. Some classification systems have focused on individual case reports and were based on nosologic aspects; others have made a distinction according to the various patterns of inheritance. 3 6 23 24 In recent studies, Szlyk et al. 7 and Yagasaki et al. 8 made use of full-field ERGs, dark adaptometry, and modified perimetric techniques to identify functionally distinct subtypes of CRD. Finally, over the past few years, a molecular genetic classification of CRD has emerged.  At the moment, four genes and three loci have been implicated in autosomal dominant CRD, whereas one X-linked locus has been described. 25 26 27 28 29 30 31 32 Thus far, two loci and one gene (ABCA4) have been associated with autosomal recessive CRD. 12 33 34 The genetic heterogeneity seen in CRD is matched by the range of the clinical findings attributed by various investigators to this type of retinal dystrophy.  Whatever the classification system used, some patients display retinal disorders that cannot be classified satisfactorily. Often, these retinal degenerations involve overlapping features. Krill et al. 5 reported that 9 of 45 patients with cone degenerations showed typical features associated with fundus flavimaculatus. Heckenlively 2 described 76 patients with cone–rod patterns on the ERG in whom retinal disease otherwise met the standard definition of RP (progressive peripheral visual field loss with ring scotoma). Alternatively, as seen in patient 10125 in this study, patients with STGD have been described who had progressive peripheral retinal degeneration with severe abnormalities in the ERG and electro-oculogram (EOG) later in life—a condition that has been described by Fishman 4 as secondary progressive cone–rod dysfunction.  The association of CRD and a dark choroid has also been described previously. 35 36 The atypical pattern of retinal degeneration with confluent patches of chorioretinal atrophy in patient 9378 resembles that in another previously described unrelated patient with CRD-like disease caused by mutations in ABCA4. 37 In the molecular genetic study by Maugeri et al., 14 in which 11 of the 12 patients with autosomal recessive CRD described in this study were analyzed, ABCA4 mutations were found in 13 of 20 unrelated patients, strongly suggesting that ABCA4 mutations are the major cause of this disorder. If this is true, the genetic heterogeneity in autosomal recessive CRD, compared with, for example, classic RP, is surprisingly low. Because autosomal recessive inheritance is believed to be the most frequent mode of inheritance of monogenic chorioretinal disorders, it is very possible that a large fraction of the patients with CRD who have been clinically studied previously carry ABCA4 mutations. In that case, the explanation for the high variability of the clinical findings in autosomal recessive CRD would not be genetic heterogeneity but rather the genotype–phenotype model for ABCA4. According to this model, there is an inverse relationship between the presumed residual ABCA4 function as an N-retinylidene-PE flippase and the severity of the disorder. 12 37 38 As a consequence, a continuum of phenotypes is to be expected, ranging from STGD to CRD to RP. Although this is probably a simplified representation of reality and needs corroboration by detailed biochemical studies of individual mutations, as described previously, this model explains why mutations in the ABCA4 gene could give rise to phenotypes that do not satisfy the standard classification of retinal dystrophies. 39   Two patients in this study may reflect borderline CRD phenotypes. Patient 9553 carries a combination of a mild (2588G>C) and severe ABCA4 mutation, which, according to the genotype–phenotype model described earlier, should be associated with STGD. We have previously discussed that most likely, one of the pathologic mutations has not yet been identified in this patient. 14 However, the age of onset in this patient (25 years) is relatively high, and although other features such as visual acuity, perimetry, and ERG findings are typical of CRD, this may indicate a relatively mild subtype. Another more convincing example of blending of ABCA4-associated phenotypes is patient 10125. The molecular findings in this patient have not yet been described elsewhere. He carries a severe splice site mutation (IVS30+1G→T) in combination with a nucleotide change leading to a stop codon at Gln1029. A patient with RP who was homozygous for the IVS30+1G→T mutation has been described, 12 whereas the Q1029X mutation has not been described. Both mutations can be considered to be null alleles. According to the proposed ABCA4 model, the clinical phenotype in patient 10125 should be RP. Instead, this patient exhibits a typical retinal dystrophy, which gradually progresses from STGD to a more widespread degeneration of photoreceptors in a cone–rod pattern later in life. At present, both rod and cone ERG responses are not detectable, indicative of a final stage similar to that in many patients with RP. Functional studies are necessary to clarify whether these specific ABCA4 mutations are responsible for the particular progression of the retinal degeneration in this patient, or whether other as yet unknown modifying factors play a role.  In this study we have described 12 unrelated patients with retinal dystrophy resembling CRD caused by mutations in the ABCA4 gene. In a previous study we described the ophthalmic features in five siblings with CRD-like retinal dystrophy who were carrying ABCA4 mutations. 37 From the clinical data of these patients and previous molecular studies in patients with autosomal recessive CRD, two important conclusions can be drawn. 12 14 First, the genetic basis of autosomal recessive CRD is less heterogeneous than was thought, based on the variability in clinical features, because mutations in the ABCA4 gene seems to be the major pathologic cause. Second, given the wide clinical spectrum of CRD-like phenotypes associated with ABCA4 mutations, detailed clinical subclassifications are difficult and may not be very useful.   Supported by the British Retinitis Pigmentosa Society, the Rotterdamse Vereniging Blindenbelangen, the Algemene Nederlandse Vereniging ter Voorkoming van Blindheid, the Stichting Blindenhulp, the Stichting de Drie Lichten, the Gelderse Blindenvereniging and the Landelijke Stichting voor Blinden en Slechtzienden and the Stichting voor Ooglijders.  Submitted for publication June 15, 2001; revised December 21, 2001; accepted January 2, 2002.  Commercial relationships policy: N.  The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.  Corresponding author: B. Jeroen Klevering, Department of Ophthalmology, University Medical Centre Nijmegen, PO Box 9101, 6500 HB, Nijmegen, The Netherlands; b.klevering@ohk.azn.nl. Table 1. View Table Patients with Cone–Rod Degeneration and ABCA4 MutationsTable 1. Patients with Cone–Rod Degeneration and ABCA4 Mutations Patient Sex Current Age (ys) ABCA4 Mutations* Visual Acuity Age of Onset (ys) Fundoscopy Color Vision Perimetry ERG Cone (μV), † ERG Rod (μV), † OD OS OD OS OD OS 9250 M 30 1622T→C; 3113C→T 194G→A CF CF 6 Pigment clumping in the macula NP Large central scotoma over 40° ND, ‡ ND, ‡ 9303 M 21 1622T→C; 3113C→T 20/400 20/400 7 Granular pigmentary changes in the macula Diffusely disturbed Central scotoma of 20° Severely decreased, § Severely decreased, § 9369 F 40 6601-6602deIAG LP LP 8 Irregular hypopigmentation, mainly in the posterior pole. In later stages: attenuated vessels and bone spicula temporal to the macula Red-green defect Central scotoma varying from 10–30° 65 (65%) 80 (80%), ∥ 140 (90%) 160 (nl), ∥ 9370 M 15 1622T→C; 3113C→T 20/200 20/200 7 Granular aspect of the macula NP Concentric central scotoma of 8° 10 (13%) 9 (13%), ¶ 29 (29%) 29 (23%), ¶ 9371 M 38 1622T→C; 3113C→T 1622T→C;3113C→T 20/400 20/400 10 Bull’s eye maculopathy Red-green defect Concentric central scotoma of 20° NP 29 (16%), ‡ NP 54 (30%), ‡ 9378 F 50 768G→T CF CF 12 Bull’s eye maculopathy, narrow vessels in periphery with mild granular changes of the pigment epithelium and confluent patches of chorioretinal atrophy Severely disturbed Large, absolute, paracentral scotomas, relative scotoma centrally 20 (20%) 30 (30%), ∥ 70 (47%) 90 (60%), ∥ 9553 F 45 2588G→C IVS35del-2→+2del4 20/400 20/400 25 Bull’s eye maculopathy. Peripheral diffuse motting of RPE Severely disturbed Large central scotoma over 40° 14 (14%) 19 (19%), ¶ 41 (41%) 24 (24%), ¶ 9633 M 22 1622T→C; 3113C→T 4469G→A 20/400 20/200 12 Atrophy of retinal pigment epithelium in posterior pole. Early stages of bull’s eye maculopathy Red-green defect Central scotoma of 20° 12 (16%) 12 (16%), ¶ 61 (62%) 39 (39%), ¶ 9650 F 20 3364G→A 20/400 20/400 5 Central granular aspect Red-green defect Large central scotoma of 30° and relative constriction of III-4 70 (39%) 106 (59%), ‡ 272 (nl) 115 (76%), ‡ 10125 M 30 IVS30+1G→T 3085C→T 20/200 20/200 8 Central hypopigmentation with dark surrounding, resembling bull’s eye. Later in life: peripheral changes characteristic of RP Severe red-green defect; mild blue-yellow defect Central scotoma of 10–15° with mild peripheral restriction 75 (75%) 80 (80%), ∥ 130 (87%) 140 (93%), ∥ 11872 M 30 634C→T 20/200 20/200 10 Bull’s eye pattern Severely disturbed; blue-yellow more than red-green Central scotoma of 25° 23 (23%) 35 (35%), ∥ 110 (73%) 95 (63%), ∥ 13163 M 15 1622T→C;3113C→T IVS36+1G→A 20/400 20/200 6 Granular aspect of retinal pigment epithelium in macula. Slightly pale optic disc Severely disturbed Central scotoma of 10–15,° no peripheral involvement ND, ¶ ND, ¶  CF, count fingers; LP, light perception; ND, not detectable; NP, not performed. *  Allele 1, first line; allele 2, second line. †  Between parentheses: percentage of the ERG value compared to the lower limit of the normality; normal ERG values are indicated nl. ‡  Minimal values for ERG recordings: 150 μV for the photopic ERG, 180 μV for the scotopic ERG. §  ERG performed with skin electrodes. ∥  Minimal values for ERG recordings: 100 μV for the photopic ERG, 150 μV for the scotopic ERG. ¶  Minimal values for ERG recordings: 99 μV for the photopic ERG, 75 μV for the scotopic ERG. Figure 1. View OriginalDownload Slide (A–D) Fundus photographs and fluorescein angiograms in eyes of patients with (atypical) CRD. (A) Patient 11872 with bull’s eye maculopathy. (B) Patient 9369, demonstrating CRD in the later stages with attenuation of the retinal arterioles and irregular pigmentation temporal to the macula. (C) Fluorescein angiograms in patient 9378 showing confluent patches of chorioretinal atrophy. (D) Patient 10125 with central hypofluorescence enclosed by an ellipsoid hyperfluorescent area. In the surrounding area, hyperfluorescent flecks are visible, and the choroidal background fluorescence seems blocked, as seen in STGD.

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ABCA4

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