Original Article Genome-Wide Linkage Analyses to Identify Loci for Diabetic Retinopathy

Hyperglycemia and long duration of diabetes are widely recognized risk factors for diabetic retinopathy, but inher-ited susceptibility may also play a role because retinopathy aggregates in families. A genome-wide linkage analysis was conducted in 211 sibships in which>2 siblings had diabetes and retinal photographs were available from a longitudinal study. These sibships were a subset of 322 sibships who had participated in a previous linkage study of diabetes and related traits; they comprised 607 diabetic individuals in 725 sibpairs. Retinal photographs were graded for presence and severity of diabetic retinopathy according to a modifi-cation of the Airlie House classification system. The grade for the worse eye was adjusted for age, sex, and diabetes duration and analyzed as a quantitative trait. Heritability of diabetic retinopathy in this group was 18 % (95 % C