Retinitis Pigmentosa and Polydactyly in a Patient with a Heterozygous Mutation on the BBS1 Gene

To report retinitis pigmentosa and a history of polydactyly in a Bardet-Biedl syndrome mutation carrier.

A 25-year-old male presented to the clinic complaining of poor visual acuity since childhood, night-blindness, and progressive peripheral vision loss. The patient also had a history of polydactyly in both feet. Ophthalmic evaluation was remarkable for a best-corrected visual acuity of 20/400 in both eyes. Imaging revealed a "salt-and-pepper" appearance surrounding the macula, bone-spicule retinal pigment epithelium hyperplasia, paravenous retinal pigment epithelium hyperplasia, and arteriolar attenuation. In addition, bilateral macular autofluorescence with a surrounding granular hypoautofluorescence and an additional hyperautofluorescent zone was present. Full-field ERG results showed non-recordable scotopic ERG responses and diminished photopic ERG responses OU, consistent with progressive rod-cone dystrophy. Genetic testing was positive for a pathogenic heterozygous mutation in the BBS1 gene of the variant c.1169T>G (p.Met390Arg) and several variants of uncertain significance in other genes.

Ascertainment of the inheritance patterns in BBS is an evolving discussion. Our case, a BBS carrier with retinitis pigmentosa and a history of polydactyly, could support previous research suggesting non-Mendelian genetics in this ciliopathy. Furthermore, genetic testing and analyses of additional mutations and variants of uncertain significance could potentially explain the reason for BBS-like phenotype in presumed BBS carriers.