While this is the most common genetic cause of PD, based on the latest information coming from the ROPAD study showing a 10.4% positive GBA1 variant among 12,580 patients with PD [30], given the estimated number of patients in the USA suffering from PD being more than 1 million [31], this 10.4% falls within the definition of rare disease, which is less than 200,000 (https://www.fda.gov/patients/rare-diseases-fda accessed on 14 February 2025). The gene discussed is GBA1; the disease is Parkinson disease.