Abstract
Abstract: :
Purpose: To characterize the clinical and electroretinographic features of patients with Stargardt's disease exhibiting coding sequence variations in the ABCA4 gene Methods: Review of 75 patients with the clinical diagnosis of Stargardt's/fundus flavimaculatus from the University of Iowa Department of Ophthalmology and Visual Sciences (41) and the Casey Eye Institute (34). Clinical examination, Goldmann perimetry and ERGs were performed on all 75 patients. Patients were divided into three groups on the basis of their electroretinographic features: (1) a normal ERG by the standards of the laboratory; (2) minimal rod or cone abnormalities; (3) severe ERG dysfunction. The latter category was further subdivided on the basis of a cone dominated loss of function (C≷R or "cone-rod dystrophy") or diffuse depression of rods and cones (C=R). Mutational analysis of the coding sequence of the ABCA4 gene was performed by single strand conformation polymorphism analysis (SSCP) followed by automated DNA sequencing. Results: Overall, 55/75 patients (and 75/150 alleles) exhibited coding sequence variations that were compatible with high-penetrance disease causing mutations. The most common of these were frameshift mutations(7), Ala1038Val (7), Pro1380Leu (6). No correlation was observed between specific sequence variations and the electroretinographic characteristics or fundus appearance. However, a significantly greater fraction of patients with normal ERG studies did not exhibit detectable disease causing coding sequence variations in the ABCA4 gene identified on either allele (p=0.0006). Conclusion: STGD/FF patients exhibit a wide range of electroretinographic abnormalities, some of which are more prevalent than previously suspected. No correlation between clinical appearance, electrophysiologic characteristics and specific ABCA4 alleles could be identified, though a significantly lower number of patients with a normal ERG exhibited detectable coding sequence variations in the ABCA4 gene. The presence of electrophysiologic dysfunction is not uncommon in Stargardt's disease and may be predictive of a poorer long term visual prognosis. Thus, electrophysiologic studies are still indicated as part of the examination of a patient with STGD.
Keywords: 562 retinal degenerations: hereditary • 395 electroretinography: clinical • 417 gene/expression