Purpose: To describe the clinical expressions, with emphasis on electrophysiological examinations, in two Swedish families with Stargardt's macular dystrophy (STGD1).
Methods: Two pairs of siblings with STGD1, for whom diagnosis had been confirmed by genetic linkage to the ABCA4 gene region, were examined regarding visual acuity, kinetic perimetry, fundus photography, full-field ERG and multifocal ERG (MERG). Possible disease-causing mutations were screened for by DNA sequencing of selected regions of the ABCA4 gene.
Results: All STGD1 patients had visual acuity 0.07-0.1. The two families presented different fundus appearances, MERGs and implicit times on 30 Hz flicker white light full-field ERGs. Genetic analysis revealed one unique sequence variation in exon 19 of the ABCA4 gene, in one allele from the patients of one of the families. This point mutation causes the amino acid substitution T972N in the ABCR protein.
Conclusion: Two pairs of siblings with STGD1 presented two different expressions of the disease regarding the distribution of the retinal dysfunction. One possible molecular explanation to the different clinical expressions may be the T972N substitution present in the ABCR protein in one of the STGD1 families investigated.