Taking our data alongside the only other published study of LRRK2 in idiopathic RBD,17 no mutations have been found in a combined total of 261 patients with RBD, substantially less than the prevalence of around 3% seen in sporadic PD.39 This provides further evidence that LRRK2-PD is associated with a lower incidence of RBD in the prodromal phase of the disease. Here, LRRK2 is linked to Parkinson disease.