Our findings could serve as a proof of concept that linking genotype data to medical-record information might be useful for estimating clinical penetrance of relatively uncommon genotypes associated with common diseases, for example, the estimation of neurologic disease in individuals harboring glucocerebrosidase (GBA [MIM: 606463]) variants, which have been found to cause Parkinson disease in Ashkenazi Jews,28 or the contribution of BRCA1 (MIM: 113705) and BRCA2 (MIM: 600185) variants to the development of breast cancer in the general population. The gene discussed is GBA1; the disease is breast cancer.