Objectives: To clinically characterize the retinal abnormalities and identify the mutation causing an autosomal dominant cone degeneration in an African American family.
Methods: Clinical characterization of family members using fundus photography, fluorescein angiography, and electrophysiological testing. Standard molecular genetic methods were used, including segregation analysis and DNA sequencing of candidate genes. Genetic mutation screening was performed in 20 individuals: 10 clinically unaffected and 10 affected.
Results: The affected family members had findings consistent with a primary cone degeneration. A novel mutation, P575L, was found in exon 8 of the GUCY2D gene in 12 members of this family.
Conclusions: In addition to finding a previously undescribed mutation in GUCY2D, 2 of the family members who were thought to be unaffected through routine clinical examinations also had this mutation. These findings suggest that autosomal dominant cone degeneration in this family demonstrated age-dependent penetrance, which appears incomplete. This is the first African American family reported with a mutation in GUCY2D. Because the disease in this family and the one we previously described is primarily a cone degeneration, this disease should be more properly classified as cone degeneration and be called cone degeneration 2.
Clinical relevance: This study helps to expand the phenotype of the disease and help clinicians identify patients with cone degenerations.