For those identified for possible presymptomatic PD, such as individuals with PD-associated GBA, LRRK2, and parkin alleles or those with RBD, more frequent measurements may detect if protective therapies, many of which are currently in development and some of which will be more effective for particular PD subtypes and patients, are effective for that patient. The gene discussed is LRRK2; the disease is Parkinson disease.