The parallel computational algorithm for detecting rare homozygous stop-gain mutations from “bulk data” (i.e. ~5000 research exomes in the BHCMG database, including this pilot study), identified a rare homozygous stop-gain mutation in GNB5 (MIM 617182) in a study participant with DD, hypotonia, retinopathy, and Mobitz type I atrioventricular block (Fig. 3a). This evidence concerns the gene GNB5 and retinal disorder.