A study based in the Netherlands has found that genetic differences between siblings with Stargardt’s disease are a prevalent phenomenon. This finding complicates sibling-based prognosis of the disease and any previous genotype-phenotype correlations. Researchers noted substantial differences in age of onset and time to develop severe visual impairment. Their findings were presented at ARVO 2019 in Vancouver earlier this year.

The study investigated inter-sibling phenotypic concordance in Stargardt’s disease among 17 families. In five, the age of onset ranged from 13 to 39 years. Median best-corrected visual acuity (BCVA) at baseline was 0.60 LogMAR (20/80 Snellen) in the right eye, and 0.50 LogMAR (20/63 Snellen) in the left. Disease duration–matched BCVA was investigated in 12 families, and the median difference was 0.41 LogMAR for the right eye and 0.41 LogMAR for the left.

In seven families, the time to develop severe visual impairment ranged from one to 29 years. Median central retinal atrophy area was 11.38mm2 in the right eyes and 10.59mm2 in the left and was highly comparable between siblings. Similarly, fundus autofluorescence and SD-OCT phenotypes were highly comparable between siblings.

Researchers conclude that phenotypic discordance within siblings with Stargardt’s disease has important implications for patient care and management.

Valkenburg D, Runhart EH, Bax NM. Highly variable disease courses in siblings with Stargardt disease. Ophthalmology. July 16, 2019. [Epub ahead of print].