Dominantly inherited macular dystrophy with flecks (Stargardt)

MACULAR ATROPHY AND PHENOTYPIC VARIABILITY IN AUTOSOMAL DOMINANT STARGARDT-LIKE MACULAR DYSTROPHY DUE TO PROM1 MUTATION

PURPOSE

To describe the phenotypic variability and rates of progression of atrophy in patients with PROM1 -associated macular dystrophy.

METHODS

Patients in this retrospective, longitudinal case series from a tertiary center had clinical examination and multimodal imaging performed. Areas of retinal pigment epithelium and ellipsoid zone loss over time by optical coherence tomography were calculated by two independent graders.

RESULTS

Fifteen patients from five kindreds with an Arg373Cys mutation in PROM1 were studied. The average age was 39 years, and 80% were women. The visual acuity was 20/40 at presentation and 20/57 at last follow-up (average 4.8 years). Three distinct macular phenotypes were observed: 1) central geographic atrophy (13%), 2) multifocal geographic atrophy (20%), and 3) bull's eye maculopathy (67%). The overall rate of atrophy progression was 0.36 mm 2 /year, but the average rate of atrophy progression varied by macular phenotype: 1.08 mm 2 /year for central geographic atrophy, 0.53 mm 2 /year for multifocal geographic atrophy, and 0.23 mm 2 /year for bull's eye maculopathy.

CONCLUSION

Patients with PROM1 -associated macular dystrophy demonstrate distinct phenotypes, with bull's eye maculopathy being the most common. The average rate of atrophy progression may be similar to reported rates for ABCA4 -related Stargardt disease and less than age-related macular degeneration. These results provide important measures for following treatment response in future gene and stem cell-based therapies.

INSIGHTS INTO AUTOSOMAL DOMINANT STARGARDT-LIKE MACULAR DYSTROPHY THROUGH MULTIMODALITY DIAGNOSTIC IMAGING

PURPOSE

Autosomal dominant Stargardt-like macular dystrophy is a rare juvenile macular dystrophy most commonly because of mutations in ELOVL4 and PROM1 genes. In this study, we review a series of cases of Stargardt-like macular dystrophy and use advanced imaging techniques to describe pathophysiologic manifestations.

METHODS

A retrospective medical record review was performed for five patients from two families with ELOVL4 mutation and one patient with PROM1 mutation including reviewing diagnostic imaging, such as fundus photography, spectral domain optical coherence tomography, fundus autofluorescence, and adaptive optics flood-illuminated photography.

RESULTS

All patients had reduced central visual acuity with varying degree of foveal atrophy. In the ELOVL4 group, best-corrected visual acuity ranged from 20/25 to 20/200. Early pathologic changes included thickening of the external limiting membrane and outer nuclear atrophy followed by retinal pigment epithelium loss in later stages. Adaptive optics imaging revealed photoreceptor loss even in early stages with good visual acuity. The PROM1 patient also had similar central vision loss with significant outer nuclear atrophy. In contrast to ELOVL4 mutation, there was more diffuse and patchy retinal pigment epithelium loss throughout the macula.

CONCLUSION

Both ELOVL4- and PROM1-related maculopathies are characterized by progressive photoreceptor atrophy and central vision loss. Using advanced diagnostic imaging, early disease changes and disease progression can be characterized.

Mimickers of age-related macular degeneration

In the Western World, the leading cause of irreversible blindness is Age- Related Macular Degeneration (ARMD). It can have significant visual impairment, and it is important that the practicing ophthalmologist is knowledgeable in the diagnosis and treatment of ARMD. Equally important is knowledge in the diagnosis of other disease entities that may mimic ARMD, as this may change the prognosis, treatment and visual outcome of patients. This article discusses those diseases that mimic ARMD and their distinguishing features.

Analysis of retinal flecks in fundus flavimaculatus using high-definition spectral-domain optical coherence tomography

PURPOSE

To assess morphologic changes associated with retinal flecks in fundus flavimaculatus using spectral-domain optical coherence tomography (SD-OCT).

DESIGN

Observational case series.

METHODS

Simultaneous recordings of SD-OCT and confocal scanning laser ophthalmoscope (cSLO) fundus autofluorescence images were obtained in fundus flavimaculatus patients. Morphologic aspects of the retinal flecks were analyzed and classified.

RESULTS

Thirty-one eyes of 17 consecutive patients (8 male, 9 female; mean age 47.9 +/- 17.1 years) were included for analysis. SD-OCT revealed 5 distinct types of lesions. Group A lesions were limited to the outer segment (OS) of the photoreceptors, the retinal pigment epithelium (RPE) interdigitations, and the RPE/Bruch membrane complex. Group B showed a protrusion of the hyper-reflective material through the interface of inner segment (IS)/OS of the photoreceptors up to the external limiting membrane. A further protrusion of the hyper-reflective material into the outer nuclear layer was seen in group C lesions. Group D lesions were characterized by an accumulation of the hyper-reflective material limited to the outer nuclear layer. Type E lesions can be described as drusen-like retinal pigment detachments. No significant correlation between the different types of flecks and visual acuity was observed (P > .05).

CONCLUSIONS

SD-OCT allows one to distinguish at least 5 different types of lesions associated with retinal flecks in fundus flavimaculatus. The ability to characterize the different types of flecks and to analyze the photoreceptor layers surrounding these lesions suggests that SD-OCT might have a potential clinical role in the evaluation and follow-up of the structural changes in fundus flavimaculatus.

DHA supplementation for late onset Stargardt disease: NAT-3 study

Background:

We analyzed the effects of a docosahexaenoic acid (DHA) supplementation in patients affected with late onset Stargardt disease (STGD).

Methods:

DHA (840 mg/day) was given to 20 STGD patients for six months. A complete ophthalmologic examination, including best-corrected visual acuity (BCVA) and multifocal electroretinogram (mfERG), was performed at inclusion day 0 (D0) and at month 6 (M6).

Results:

Overall, no statistical differences have been observed at M6 vs D0 as regards BCVA and mfERG (P > 0.05). Mild Improvement of BCVA and improvement of mfERG was noted in seven/40 eyes of four/20 patients. In the first patient, the peak of the a wave increased from 66 nV/deg² to 75.4 nV/deg² in the right eye (RE) and 24.5 nV/deg² to 49.1 nV/deg² in the left eye (LE). The peak of the b wave improved from 122 nV/deg² to 157 nV/deg² in the RE, and 102 nV/deg² to 149 nV/deg² in the LE. In the second patient peaks of the a and b waves respectively increased from 11.8 nV/deg² to 72.1 nV/deg² and 53 nV/deg² to 185 nV/deg² in the RE. In the third patient the peak of the a wave increased from 37 nV/deg² to 43 nV/deg² in the RE, and from 31 nV/deg² to 45 nV/deg² in the LE; the peak of the b wave improved from 70 nV/deg² to 89 nV/deg² in the RE, and from 101 nV/deg² to 108 nV/deg² in the LE. In the fourth patient, the peak of the a wave increased from 39 nV/deg² to 42 nV/deg² in the RE, and from 40 nV/deg² to 43 nV/deg² in the LE; the peak of the b wave improved from 86 nV/deg² to 94 nV/deg² in the RE, and from 87 nV/deg² to 107 nV/deg² in the LE.

Conclusion:

DHA seems to influence some functional parameters in patients affected with STGD. However, no short-term benefit should be expected from DHA supplementation.

Genetics and molecular pathology of Stargardt-like macular degeneration

Stargardt-like macular degeneration (STGD3) is an early onset, autosomal dominant macular degeneration. STGD3 is characterized by a progressive pathology, the loss of central vision, atrophy of the retinal pigment epithelium, and accumulation of lipofuscin, clinical features that are also characteristic of age-related macular degeneration. The onset of clinical symptoms in STGD3, however, is typically observed within the second or third decade of life (i.e., starting in the teenage years). The clinical profile at any given age among STGD3 patients can be variable suggesting that, although STGD3 is a single gene defect, other genetic or environmental factors may play a role in moderating the final disease phenotype. Genetic studies localized the STGD3 disease locus to a small region on the short arm of human chromosome 6, and application of a positional candidate gene approach identified protein truncating mutations in the elongation of very long chain fatty acids-4 gene (ELOVL4) in patients with this disease. The ELOVL4 gene encodes a protein homologous to the ELO group of proteins that participate in fatty acid elongation in yeast. Pathogenic mutations found in the ELOVL4 gene result in altered trafficking of the protein and behave with a dominant negative effect. Mice carrying an Elovl4 mutation developed photoreceptor degeneration and depletion of very long chain fatty acids (VLCFA). ELOVL4 protein participates in the synthesis of fatty acids with chain length longer than 26 carbons. Studies on ELOVL4 indicate that VLCFA may be necessary for normal function of the retina, and the defective protein trafficking and/or altered VLCFA elongation underlies the pathology associated with STGD3. Determining the role of VLCFA in the retina and discerning the implications of abnormal trafficking of mutant ELOVL4 and depleted VLCFA content in the pathology of STGD3 will provide valuable insight in understanding the retinal structure, function, and pathology underlying STGD3 and may lead to a better understanding of the process of macular disease in general.

In vivo visualization of photoreceptor layer and lipofuscin accumulation in stargardt's disease and fundus flavimaculatus by high resolution spectral-domain optical coherence tomography

INTRODUCTION

To assess photoreceptor (PR) layer morphology in patients with Stargardt's disease (STGD) and fundus flavimaculatus (FFM) using high resolution spectral domain optical coherence tomography (HD-OCT; OCT 4000 Cirrus, Humphrey-Zeiss, San Leandro, CA).

METHODS

This was a prospective observational case series. Sixteen consecutive patients with STGD and FFM underwent a complete ophthalmologic examination. Optical coherence tomography examination was performed with HD-OCT, a high-speed (27,000 axial scans per second) OCT system using spectral/Fourier domain detection, with an axial image resolution of 5 mum.

RESULTS

A total of 31 eyes were included in the study. Transverse loss of the PR layer in the foveal region was shown by HD-OCT. Twenty eyes with clinically evident central atrophy had a disruption of either the Verhoeff's membrane (VM) or the layer corresponding to the interface of inner segment (IS) and outer segment (OS) of PR in the foveal region. Among these eyes, 12/20 eyes had a loss of the PR layer (loss of both VM and IS-OS interface) in the foveal region. Eleven eyes (11/31) without clinically evident central atrophy had an intact interface of IS and OS of PR centrally. Moreover, we observed hyperreflective deposits: type 1 lesions located within the retinal pigment epithelium (RPE) layer and at the level of the outer segments of PR, and type 2 lesions located at the level of the outer nuclear layer and clearly separated from the RPE layer. Type 1 lesions alone were associated with absence of loss of the PR layer in the foveal region in all eyes; type 2 lesions were always associated with presence of type 1 lesions, and often (8/12 eyes) associated with loss of the PR layer within the foveal region. Mean best-corrected visual acuity (BCVA) was significantly correlated with loss of the PR layer in the foveal region (P < 0.001), as well as to presence of type 2 flecks (P = 0.03).

CONCLUSION

Type 2 deposits in STGD/FFM patients seem to represent a marker of the possible evolution towards foveal atrophy.

Correlation of visual function impairment and OCT findings in patients with Stargardt disease and fundus flavimaculatus

PURPOSE

To investigate the relationship between morphologic lesions of the retina and functional abnormalities in patients with Stargardt disease (STGD) and fundus flavimaculatus (FFM). DESIGN. Case-controlled, prospective, comparative observational study.

METHODS

A complete ophthalmologic examination, including best-corrected visual acuity (BCVA) and optical coherence tomography (OCT), was performed in 61 eyes of 32 consecutive patients with STGD/FFM and in 60 eyes of 30 matched healthy control subjects. Furthermore, fundus-related perimetry was performed in 12 of the affected eyes.

RESULTS

The age ranged from 21 to 71 years in STGD/FFM patients and from 21 to 72 years in controls. BCVA ranged from 20/20 to 20/400 and from 20/20 to 20/32, respectively, in STGD/FFM patients and in controls. A foveal thinning was found by OCT Stratus in almost all cases (average 160 microm) compared with controls (average 210 microm) (p<0.001). BCVA impairment significantly correlated to the degree of foveal thinning (r2=0.16; p=0.0014). Moreover, in STGD/FFM patients the authors observed two types of hyperreflective deposits which were not correlated with BCVA impairment or foveal thinning. In addition, fundus-related perimetry revealed a stable fixation in 8/12 eyes, that was predominantly central in only 4 of these eyes. A smaller degree of foveal thinning correlated to a more stable fixation (p=0.0108), even if not predominantly central (p=0.0218).

CONCLUSIONS

In this series, lower visual acuity and unstable fixation correlated with a greater transverse foveal thinning. OCT and fundus-related perimetry may be useful tools in STGD/FFM patients.

Intrafamilial clinical heterogeneity associated with a novel mutation of the retinal degeneration slow/peripherin gene

AIMS

To identify the phenotypic variations in 6 related individuals affected by a novel mutation in the retinal degeneration slow/peripherin gene.

METHODS

Ten family members underwent ophthalmologic assessment with slit-lamp biomicroscopy, dilated fundus examination, fundus photography, autofluorescence imaging and electrophysiological tests. Genomic DNA was extracted from blood samples of all family members (n = 15) using the standard salting-out procedure.

RESULTS

The novel C165R mutation was identified in 8 individuals. Of these 8 patients, only 6 gave consent to the clinical study. They had a retinal disease characterized by an adulthood onset of symptoms, and their best corrected visual acuity was between 20/50 and 20/20. Fundus examination showed that 3 patients had typical fundus flavimaculatus: 1 had butterfly-shaped pattern dystrophy and 2 had incipient retinal changes.

CONCLUSION

We identified a novel mutation of the retinal degeneration slow/peripherin gene in a family affected by different patterns of retinal dystrophy. This is the first report of an association of fundus flavimaculatus with butterfly-shaped pattern dystrophy.

Analysis of retinal flecks in fundus flavimaculatus using optical coherence tomography

BACKGROUND/AIM

Retinal flecks are commonly observed in both Stargardt disease and fundus flavimaculatus (FFM). The aim was to determine the precise localisation of these flecks within the retinal layers using Stratus optical coherence tomography (OCT).

METHODS

A prospective observational case series. A complete ophthalmological examination, including autofluorescence, fluorescein angiography (FA), and Stratus OCT (Carl Zeiss) was performed in 49 eyes of 26 consecutive patients with FFM. Six to 12 Stratus OCT linear scans focused on the retinal flecks were performed in each eye.

RESULTS

The age at presentation ranged from 23 years to 71 years and visual acuity ranged from 20/20 to 20/400. Hyper-reflective deposits classified into two types were observed on Stratus OCT: type 1 lesions (94% of eyes) presented as dome-shaped deposits located in the inner part of the retinal pigment epithelium (RPE) layer and type 2 lesions (86% of eyes) presented as small linear deposits located at the level of the outer nuclear layer and clearly separated from the RPE layer.

CONCLUSIONS

Stratus OCT is a non-invasive instrument that provides new information on the location of flecks in FFM. The location of type 2 lesions is quite unusual among macular dystrophies; OCT may therefore be useful in the diagnosis of retinal flecks in some cases of FFM.

Les dystrophies maculaires héréditaires

Hereditary macular dystrophies are degenerative diseases of the central area of the retina associating primary anomalies of the retinal pigment epithelium and sensory retina. These conditions, whose hallmark is a loss of visual acuity, are a major cause of blindness and affect patients at all ages. Macular dystrophies group diseases that are heterogenous at the genetic level, as well as at the clinical, histological and physiopathological levels. Monogenic macular dystrophies are rare autosomal dominant conditions, with the exception of Stargardt disease in its typical form, which is not only relatively frequent but is also inherited as an autosomal recessive trait. During the last few years, the molecular bases of these conditions have begun to be elucidated with the identification of several responsible genes. For some macular dystrophies, this new information has confirmed pre-existing hypotheses on their pathophysiology, but for others, the discovery of the disease gene has added further complexity to the disease process. Two contradictory concepts were particularly highlighted by these genetic studies. Several phenotypes previously described as different clinical entities were brought together by the identification of mutations in the same gene, and converselyome conditions that were clinically assigned the same name, often heterogeneous at the clinical level, appeared genetically and physiopathologically heterogeneous. In addition, it is worth noting that the monogenic macular dystrophy genes were often regarded as potential factors for susceptibility to age-related macular degenerations. However, to date, only ABCA4 mutations have been associated with a minority of this frequent multifactorial condition. The aim of this article is to give a progress report on the monogenic macular dystrophy genes and to review current knowledge concerning the pathophysiology of these conditions.

Autosomal dominant Stargardt-like macular dystrophy

Autosomal dominant Stargardt-like macular dystrophy is one of the early onset macular dystrophies. It is characterized clinically in its early stages by visual loss and by the presence of atrophic macular changes with or without the presence of yellowish flecks. It is an important retinal dystrophy to study, not only because it has implications in the care and treatment of patients with the condition, but because it also provides important information regarding retinal function. Review of the literature suggests that many of the reported families are linked to chromosome 6q. Genetic and genealogical evidence suggests that these families have descended from a common ancestor or founder. The recent identification of a disease-causing gene that is involved in fatty acid metabolism may have implications in the study of the more common age-related macular degeneration. We review the recent clinical, genetic, and genealogical aspects of autosomal dominant Stargardt-like macular dystrophy.

Genotype-phenotype correlations and differential diagnosis in autosomal dominant macular disease

In the past few years, great progress has been made in the understanding of macular diseases. A number of disease-causing genes have been cloned, and numerous loci for other conditions have been mapped. The purpose of this article is to provide an overview of the current understanding of the genotype-phenotype correlations in autosomal dominant macular diseases with an emphasis on differential diagnostic issues. Whenever possible, the molecular correlates have been reviewed and the implications for age-related macular degeneration have been discussed. The many similarities of these diseases to age-related macular degeneration of the atrophic or exudative type, which can be misleading in elderly subjects, have also been addressed. While some conditions yield disease truly confined to the macula, others show widespread retinal involvement on functional testing. Clear-cut genotype-phenotype correlations are possible only for some forms of macular diseases. To further complicate the diagnostic process, there is a considerable degree of clinical overlap between many of them, making the differential diagnostic process potentially challenging. Functional testing, careful assessment of family history and extensive family work-up are essential in differentiating at the clinical level most, but not all, of these disease entities. Awareness of all of these conditions is required to direct correctly diagnostic investigations, to formulate an accurate prognosis, and for proper genetic counseling.

A comprehensive survey of sequence variation in the ABCA4 (ABCR) gene in Stargardt disease and age-related macular degeneration

Stargardt disease (STGD) is a common autosomal recessive maculopathy of early and young-adult onset and is caused by alterations in the gene encoding the photoreceptor-specific ATP-binding cassette (ABC) transporter (ABCA4). We have studied 144 patients with STGD and 220 unaffected individuals ascertained from the German population, to complete a comprehensive, population-specific survey of the sequence variation in the ABCA4 gene. In addition, we have assessed the proposed role for ABCA4 in age-related macular degeneration (AMD), a common cause of late-onset blindness, by studying 200 affected individuals with late-stage disease. Using a screening strategy based primarily on denaturing gradient gel electrophoresis, we have identified in the three study groups a total of 127 unique alterations, of which 90 have not been previously reported, and have classified 72 as probable pathogenic mutations. Of the 288 STGD chromosomes studied, mutations were identified in 166, resulting in a detection rate of approximately 58%. Eight different alleles account for 61% of the identified disease alleles, and at least one of these, the L541P-A1038V complex allele, appears to be a founder mutation in the German population. When the group with AMD and the control group were analyzed with the same methodology, 18 patients with AMD and 12 controls were found to harbor possible disease-associated alterations. This represents no significant difference between the two groups; however, for detection of modest effects of rare alleles in complex diseases, the analysis of larger cohorts of patients may be required.

Autosomal dominant Stargardt-like macular dystrophy segregating in a large Canadian family

BACKGROUND

Inherited macular dystrophies account for a major fraction of the cases of retinal degenerative disease that lead to permanent blindness. We describe the clinical and genetic findings in a Canadian family with a form of macular dystrophy resembling autosomal dominant Stargardt-like macular dystrophy.

METHODS

Standard ophthalmologic examinations were performed in members of a single five-generation Alberta family. Tests of visual acuity and colour vision, fundus photography, fluorescein angiography and electroretinography were performed in 15 affected people. Blood was collected from 24 family members, and DNA was extracted for genotyping. Genetic linkage analysis was performed using polymorphic short tandem repeat microsatellite markers located on chromosome 6q, a region containing loci for several macular disorders.

RESULTS

Affected family members display clinical characteristics resembling autosomal dominant Stargardt-like macular dystrophy, previously assigned to chromosome 6q (STGD3). Linkage analysis generated a peak lod score of 5.50 at an estimated recombination fraction of 0.00 for marker locus D6S300.

INTERPRETATION

The family described has an autosomal dominant macular dystrophy that resembles Stargardt-like macular dystrophy. The disease locus for this family maps to an interval on chromosome 6q that overlaps that for STGD3 and other retinal dystrophy loci. These findings provide further evidence that human chromosome 6q represents a "hot spot" for retinal disorders.

Stargardt's macular dystrophy

Stargardt's disease is the most common hereditary macular dystrophy with an estimated incidence of 1 in 10000. The typical patient presents with visual symptoms between the first and third decades of life. This paper will discuss a patient who was diagnosed with Stargardt's macular dystrophy (SMD) at an older age. The clinical characteristics, functional testing, histopathology, differential diagnosis and recent genetics advances related to SMD will be discussed in this report.

Clinical and genetic studies of an autosomal dominant cone-rod dystrophy with features of Stargardt disease

Cone-rod dystrophy (CORD) and Stargardt disease (STGD) are two hereditary retinal dystrophies with similarities to age-related macular degeneration. Cone-rod dystrophies are a group of degenerative disorders resulting in decreased visual acuity and color vision, attenuated electroretinographic (ERG) responses, and atrophic macular lesions. Autosomal dominant, autosomal recessive, and X-linked forms of cone-rod dystrophy have been reported. Stargardt disease is characterized by reduced visual acuity, atrophic macular changes, prominent 'flavimaculatus flecks' in the pigment epithelium of the posterior retina, and a virtually pathognomic 'dark choroid' pattern on fluorescein angiography. Stargardt disease is classically inherited as an autosomal recessive trait, although numerous families have been described in which features of Stargardt disease are transmitted in an autosomal dominant manner. We have identified a new kindred with autosomal dominant cone-rod dystrophy with features of Stargardt-like disease. Detailed clinical evaluation, genotype analysis, and linkage analysis were performed. Fluorescein angiography revealed a 'dark choroid' pattern in three affected subjects. Electroretinography disclosed markedly reduced scotopic and photopic responses in three affected individuals. Genetic analysis revealed linkage to known loci for cone-rod dystrophy (CORD7) and Stargardt-like disease (STGD3) on chromosome 6q14. A peak lod score of 3.3 was obtained with the marker D6S280 at straight theta =0.010. A physical map was constructed by screening a YAC library with short tandem repeat markers in the region. Screening of a candidate gene, the rho1 subunit of the GABA receptor, failed to reveal any mutations.

Electrophysiological findings in Stargardt's-fundus flavimaculatus disease

PURPOSE

To determine the incidence of electrophysiological abnormalities in patients with Stargardt's-fundus flavimaculatus (STGD/FFM) disease.

METHODS

A retrospective review was carried out of the hospital records of 46 patients who had undergone a scotopic, single flash photopic and 30 Hz electroretinogram (ERG), pattern ERG (PERG) and electro-oculogram (EOG).

RESULTS

Patients were classified in two groups: those with flecks (n = 26) and those without flecks (n = 20). The incidence of abnormalities (amplitude and/or latency) for the two groups was: PERG, 90% and 98%; 30 Hz ERG, 55.8% and 50%; scotopic ERG, 38.5% and 27.5%; and single flash photopic ERG, 26% and 16%, respectively. EOG abnormalities occurred significantly more frequently in the group with flecks compared with the group without flecks: 69% and 42.5% respectively (p < 0.025). Furthermore, in the group with flecks the group mean scotopic ERG b-wave, 30 Hz ERG b-wave and PERG (P50) amplitude were significantly lower than in the group without flecks (p < 0.01).

CONCLUSIONS

The most consistent electrophysiological abnormality in STGD/ FFM is the reduction of the PERG. However, EOG, 30 Hz ERG, scotopic and photopic ERG abnormalities can also frequently occur. ERG and EOG abnormalities occur more often in the presence of flecks.

A new locus for autosomal dominant stargardt-like disease maps to chromosome 4

Stargardt disease (STGD) is the most common hereditary macular dystrophy and is characterized by decreased central vision, atrophy of the macula and underlying retinal-pigment epithelium, and frequent presence of prominent flecks in the posterior pole of the retina. STGD is most commonly inherited as an autosomal recessive trait, but many families have been described in which features of the disease are transmitted in an autosomal dominant manner. A recessive locus has been identified on chromosome 1p (STGD1), and dominant loci have been mapped to both chromosome 13q (STGD2) and chromosome 6q (STGD3). In this study, we describe a kindred with an autosomal dominant Stargardt-like phenotype. A genomewide search demonstrated linkage to a locus on chromosome 4p, with a maximum LOD score of 5.12 at a recombination fraction of.00, for marker D4S403. Analysis of extended haplotypes localized the disease gene to an approximately 12-cM interval between loci D4S1582 and D4S2397. Therefore, this kindred establishes a new dominant Stargardt-like locus, STGD4.

Autosomal dominant Stargardt-like macular dystrophy: I. Clinical characterization, longitudinal follow-up, and evidence for a common ancestry in families linked to chromosome 6q14

PURPOSE

Characterize the phenotype of autosomal dominant Stargardt-like macular dystrophy in two families linked to chromosome 6q14 and determine whether they share a common ancestry.

METHODS

Two families spanning 10 generations were identified and studied independently. Participating members were examined and genetic linkage and genotyping performed.

RESULTS

Presenting symptoms included decreased vision, hemeralopia, and mild photophobia. The subjective onset of visual loss ranged from age 3 to 50 with a mean of 14 years. A Snellen acuity of 20/200 occurred at a mean age of 22 years. Over decades, the macular lesion enlarged and visual acuity decreased to 20/300 to 20/800. The typical phenotype was well-circumscribed, homogenous atrophy of the retinal pigment epithelium and choriocapillaris in the macula, with surrounding yellow flecks and temporal optic nerve pallor. The phenotypic spectrum included a pattern dystrophy-like appearance, diffuse geographic atrophy, and extensive fundus flecks. Genotyping revealed that the two families were linked to chromosome 6q14 and shared a common haplotype spanning 21 cM between D6S430 and D6S300. The two families were subsequently shown by genealogic investigation to represent different branches of a common kindred.

CONCLUSIONS

Families with autosomal dominant Stargardt-like macular dystrophy linked to chromosome 6q14 share a common phenotype and in some cases can be distinguished from similar dystrophies by inheritance pattern and clinical features. The finding that these two families shared a common ancestor suggests the existence of a founder effect. Characterization of the gene for autosomal dominant Stargardt-like macular dystrophy may enable better understanding of this condition and elucidation of its potential role in other forms of macular degeneration.

Analysis of 21 Stargardt's disease families confirms a major locus on chromosome 1p with evidence for non-allelic heterogeneity in a minority of cases

BACKGROUND

Autosomal recessive Stargardt's disease is a macular degeneration characterised by a juvenile onset and a rapidly progressive course resulting in an atrophic macular area typically surrounded by yellowish retinal flecks.

METHOD

The disease locus has previously been assigned to markers from chromosome 1p21-p13 by genetic linkage analysis in eight multiplex Stargardt's disease families.

RESULTS

In an extended analysis, the assignment to chromosome 1p was confirmed in the majority of the 21 families with Stargardt's disease who were studied. In addition, a series of recombinant chromosomes further narrowed the Stargardt's disease region to an approximately 3 cM interval between markers at D1S424 and D1S497.

CONCLUSION

Multipoint linkage analysis most probably excludes this locus in three of these families suggesting non-allelic heterogeneity with at least one additional minor Stargardt's disease locus.

The variable expressivity of a family with central areolar pigment epithelial dystrophy

PURPOSE

To clarify the nosology of autosomal dominant central areolar pigment epithelial dystrophy (CAPED) as previously described.

METHODS

The authors studied a family of 69 members spanning six generations with a macular dystrophy. Thirty-four patients were examined, and those found to be affected underwent further testing, including visual fields, electrophysiologic studies, and fluorescein angiography. Family history and medical records were used in three additional deceased patients.

RESULTS

Eleven patients were identified as having CAPED. The phenotype was inherited in an autosomal dominant fashion. Six of these patients were examined by us and had mid-life onset (at 32-53 years) of progressive visual loss (20/50--counting fingers), occurring over a 3- to 10-year period. These subjects had circumscribed hypopigmented maculae, retinal pigment epithelial window defects on fluorescein angiography, central scotomas, and electrophysiologic studies, ranging from normal to severely abnormal. Three deceased patients were presumed to have CAPED by review of records or family history. Two additional patients examined had mild macular changes but good visual acuity and no significant abnormalities on electrophysiologic studies. The latter two patients are presumed to have had early manifestations of CAPED.

CONCLUSION

This family demonstrates that CAPED is an autosomal-dominant hereditary macular dystrophy which has late-onset and variable expressivity.

Pattern dystrophies of the retinal pigment epithelium

Pattern dystrophies of the retinal pigment epithelium are infrequent fundus abnormalities arranged in various patterns of dots, lines and branches. The basic lesion appears to be yellow deposits of abnormal lipofuscin accumulated within degenerated retinal pigment epithelium cells. Examinations were carried out on two families who had developed different patterned alterations in the retinal pigment epithelium. The proband of family 1 had diffuse changes associated with equatorial folds. One sister had a macular alteration. A daughter was normal; a son had bilateral atrophy of the temporal retinal pigment epithelium. The proband of family 2 had bilateral, symmetrical retinal pigment epithelium lesions that simulated fundus flavimaculatus. His first daughter had a central lesion in her right eye. The second daughter, a peripapillary crescent of hyperpigmentation in her right eye, and circumpapillary chorioretinal atrophy associated with foveolar abnormalities in the left. This report provides further evidence that variable types of pattern dystrophy can occur within a single family pedigree and support the current opinion that all forms of pattern dystrophies are variants of a single pathogenic mechanism.

Genetic and molecular studies of macular dystrophies: recent developments

Macular degeneration is a heterogeneous group of disorders characterized by progressive central visual loss and degeneration of the macula and underlying retinal pigment epithelium (RPE) of the eye. Age-related macular degeneration (ARMD), the most common form of the disease, is the leading cause of legal blindness in the elderly population in the United States and in the many developed countries throughout the world. Despite its prevalence, its etiology and pathogenesis are poorly understood, and effective treatment options are limited for most patients. Inherited macular dystrophies share many important features with ARMD but are more readily studied by molecular genetic approaches. Over the past few years, significant progress has been made in the molecular genetics of inherited macular dystrophies. Genes responsible for dominant and recessive Stargardt's macular dystrophy as well as Best's disease have been localized to specific chromosomal regions. The peripherin/RDS gene when defective is associated with butterfly-shaped pattern dystrophy. Molecular studies of genes involved in macular dystrophies may yield insights into the mechanisms of pathogenesis of macular degeneration and provide new rationale for the management and treatment of patients with these diseases.

Extensive intrafamilial and interfamilial phenotypic variation among patients with autosomal dominant retinal dystrophy and mutations in the human RDS/peripherin gene

Clinical phenotypes of patients with mutations in the human RDS/peripherin gene are described. A 67-year-old woman, who carried a 1 base pair deletion in codon 307, presented with typical late onset autosomal dominant retinitis pigmentosa (RP). In another autosomal dominant pedigree, a nonsense mutation at codon 46 caused 'inverse' retinitis pigmentosa-like fundus changes associated with progressive cone-rod degeneration in a 58-year-old man, whereas his 40-year-old son presented with yellow deposits in the retinal pigment epithelial layer resembling a pattern dystrophy, and with moderately reduced rod and cone function, as determined by two colour dark adapted threshold perimetry and electroretinography. It is suggested that both clinical pictures within this latter family may represent manifestations of fundus flavimaculatus. The clinical data of the three patients provide further evidence for the remarkable variety of disease expression within and between families with mutations in the RDS/peripherin gene. Currently, the most comprehensive statement could be that RDS/peripherin mutations are associated either with typical RP or with various forms of flecked retinal disease.

Stargardt's disease/fundus flavimaculatus: psychophysical and electrophysiologic results

Retinal functions were analyzed psychophysically and electrophysiologically in 73 patients (146 eyes) with Stargardt's disease/fundus flavimaculatus. Patients were classified into types 1, 2, 3, and 4; patients with type 3 were subdivided into 3E and 3L (early and late onset of initial symptoms). Most had visual acuity (VA) of 20/200 or greater at initial testing. VA declined 0.25 octave/year during follow-up (mean, 6.1 years). Four of 16 patients (25%) older than 40 years had VA of 20/200 or less in the stronger eye. Psychophysical tests (flicker profile, central scotoma, dark adaptation) showed variable degrees of abnormalities. Electrophysiological tests showed significant photopic b-wave amplitude decreases, particularly in type 3E (42.2% of normal). The electro-oculogram light peak/dark trough ratio was abnormal in 60 of 132 eyes (45.5%), especially in type 3E (25 of 34 eyes, 73.5%). Visual prognosis and overall visual function varied depending upon disease type, location of retinal lesions, and age of onset. In Type 3E, overall retinal function was poorest and accompanied by the most severe decline of central vision and function in the surrounding macula.

Color vision in Stargardt's disease

The color vision of nine patients aged from 13 to 52 years with Stargardt's disease was studied with the following tests: Standard Pseudoisochromatic Plates part 2 (SSP2), Farnsworth-Munsell 100 hue test (FM100), Nagel (red-green) anomaloscope and Besançon (blue) anomalometer. At the beginning of the disease, a very slight defect in red-green color vision could be demonstrated. Later, a distinct acquired red (pseudo-protanomalous) defect in the Nagel anomaloscope and an abnormal error score in the FM100 test were observed. In advanced stages, the red defect became stronger (scotopization) and the FM100 test showed a red-green axis. In the course of the disease, a blue defect with the SPP2 plates and with the Besançon anomalometer could also be found. The visual acuities of the patients had a significant correlation with the matching ranges of the Rayleigh equation and the Moreland equation. The duration of the disease did not show any correlation with the color vision tests.

Genetic linkage of vitelliform macular degeneration (Best's disease) to chromosome 11q13

Macular degeneration is the most common cause of legal blindness in older patients in developed countries. Best's vitelliform dystrophy is an early-onset, autosomal dominant form of macular degeneration characterized by an egg-yolk-like collection of lipofuscin beneath the pigment epithelium of the retinal macula. Fifty-seven members of a five-generation family affected with this disease were studied. A combination of ophthalmoscopy and electro-oculography was used for diagnosis; 29 patients were found to be affected and 16 unaffected. Linkage analysis mapped the disease-causing gene to chromosome 11q13. Three markers in this region were found to be significantly linked (Zmax > 3.0) to the disease. Multipoint analysis yielded a maximum Lod score of 9.3 in the interval between markers INT2 and D11S871.

Stargardt's disease. Family studies

Three families including seven members with Stargardt's disease were examined. In addition to the affected family members, 43 of the relatives had an eye examination. In one family, there was a consanguineous marriage to be found. The heredity was most probably autosomal recessive in all of the three families. The ages of the seven patients with Stargardt's disease varied from 13 to 50 years, visual acuities from 0.05 to 1.0, and refraction from -8.5 to +2.25 D. In fundus, absent foveal reflex, atrophic macular spots and yellow perimacular flecks could be observed; one patient had also yellow flecks in the peripheral retina. In the visual fields, a central scotoma was found in five patients. Dark adaptation was abnormal in three patients and electroretinogram in one patient. All of the patients had defective red colour vision. In the fluoresceinangiogram, hyperfluorescent macular spots and dark choroid could be observed. The ophthalmological findings are discussed comparing them to the earlier observations of this disease.

Visual acuity loss in patients with Stargardt's macular dystrophy

Ninety-five patients with Stargardt's macular dystrophy were appraised for visual loss with age by both life-table analyses and cross-sectional procedures. The probability of maintaining a visual acuity of 20/40 or better in at least one eye was 52% by age 19, 32% by age 29, and 22% by age 39. In the population studied, once a patient's visual acuity dropped below 20/40, it tended to decrease rapidly and stabilize at 20/200. Fluorescein angiograms obtained on 64 of the 95 patients showed a "dark choroid" in 55 (85.9%). This finding, therefore was present in the majority of the patients, although its absence does not rule out Stargardt's macular dystrophy.