Rod-cone dystrophy in an adult with GNB1-related disorder: An expansion of the phenotype and natural history

GNB1-related disorder is characterized by intellectual disability, abnormal tone, and other variable neurologic and systemic features. GNB1 encodes the β1 subunit of the heterotrimeric G-protein, a complex with a key role in signal transduction. Consistent with its particularly high expression in rod photoreceptors, G_β1 forms a subunit of retinal transducin (G_αtβ1γ1), which mediates phototransduction. In mice, GNB1 haploinsufficiency has been associated with retinal dystrophy. In humans, however, although vision and eye movement abnormalities are common in individuals with GNB1-related disorder, rod-cone dystrophy is not yet an established feature of this condition. We expand the phenotype of GNB1-related disorder with the first confirmed report of rod-cone dystrophy in an affected individual, and contribute to a further understanding of the natural history of this condition in a mildly affected 45-year-old adult.