Clinical Polymorphism of Stargardt Disease in a Large Consanguineous Tunisian Family; Implications for Nosology

PURPOSE: To describe the polymorphic expression of Stargardt disease in a large Tunisian family with clinical intra- and interfamilial variation of the condition. METHODS: Twelve subjects from two related families with autosomal recessive Stargardt disease were enrolled. A detailed clinical examination including visual acuity and visual field measurement, fundus photography, fluorescein angiography, electroretinography (ERG) and color vision testing was performed for all subjects. RESULTS: The youngest child from family A manifested typical Stargardt disease while her two brothers presented with Stargardt disease-fundus flavimaculatus (STGD-FFM) and her two sisters demonstrated a peculiar phenotype overlapping Stargardt disease and cone-rod dystrophy; their phenotypic manifestation corresponded well with ERG groups I, II and III, respectively. This uncommon occurrence of an age-related decline in ERG amplitude and worsening of fundus changes is suggestive of a grading pattern in Stargardt disease. Their two cousins in family B, displayed the STGD-FFM phenotype. Despite clinically similar STGD-FFM patterns in both families, age of onset and progression of the phenotype in family B differed from family A. CONCLUSION: This is the first report on phenotypic variation of Stargardt disease in a large Tunisian family. Regarding phenotype and severity of visual symptoms, family A demonstrated Stargardt disease at various stages of progression. In addition, STGD-FFM appeared to be an independent clinical entity in family B. These findings imply that further parameters are required to classify Stargardt’s disease.