GBA1 and Parkinson disease: Although the proportion of PD patients with GBA1 mutations varies by ethnicity and sequencing methods used, recent studies suggested that the heterozygous status confers a cumulative risk of developing PD of 5% at age 60, rising to 15–30% at age 80 (Schapira, 2015; Balestrino and Schapira, 2018).