Mutations in LRRK2 cause autosomal dominant Parkinson’s disease (PD) with age- and mutation-dependent penetrance1–3, whereas heterozygous mutations in GBA1 are the most common genetic risk factors for PD and the cause of the lysosomal storage disorder Gaucher disease when present in homozygosis4,5. The gene discussed is GBA1; the disease is Parkinson disease.