A Novel ABCA4 Mutation Associated with a Late-Onset Stargardt Disease Phenotype: A Hypomorphic Allele

Abstract

Background: Stargardt disease (STGD) is the most common juvenile hereditary macular dystrophy. In the majority of cases, the diagnosis is made prior to 20 years of age and usually leads to loss of central vision. Late-onset STGD affects a smaller number of patients. Identifying genetic changes which could be associated with clinically important differences in severity or presentation of the disease is important for understanding the mechanisms of visual loss and for planning future therapeutic approaches. Methods: We report a patient with the classic phenotype of STGD with late-onset mild disease exhibiting a slow clinical progression over 14 months of follow-up. Results: A 37-year-old man presented with STGD and good vision of 6/24 in the right eye and of 6/6 in the left eye as well as typical electrophysiology findings. Objective and subjective visual deterioration was not noted over a period of 14 months. Macular genetic testing revealed a novel missense mutation in ABCA4 (Thr829Met) combined with Gly1961Glu, a classic STGD mutation usually associated with a moderately severe phenotype. Conclusions: It is suggested that the Thr829Met mutation could give rise to a hypomorphic allele of the ABC transporter with a resultant phenotype of comparatively mild STGD.