Expanding the Spectrum of BCAP31-Associated Diseases: Early-Onset Parkinson Disease

Hemizygous variants in B-cell receptor-associated protein 31 (BCAP31) can cause deafness, dystonia, and cerebral hypomyelination syndrome, which typically presents in infancy.

We performed whole-exome sequencing in a family with 2 affected individuals who exhibited congenital hearing loss and adult-onset motor symptoms, including Parkinson disease (PD) and cerebellar ataxia. To assess the frequency of BCAP31 variants, we analyzed 234 Japanese individuals with either recessively inherited familial PD or early-onset PD using Sanger sequencing.

Whole-exome sequencing identified a novel BCAP31 variant (c.302G>A; p.Arg101Lys) shared by both individuals. The proband developed parkinsonism in early adulthood; responded well to levodopa; and later exhibited wearing-off phenomena, dyskinesias, and cerebellar signs. Sanger sequencing of a Japanese population with PD identified 3 additional BCAP31 variants; however, all 3 variants were predicted to be benign and showed no enrichment compared with public databases.

This report links a BCAP31 variant to adult-onset PD. Our findings suggest that BCAP31 should be considered in male patients with early-onset PD and atypical features such as congenital deafness and cerebellar involvement.