ABSENCE OF LRRK2 MUTATIONS IN A COHORT OF PATIENTS WITH IDIOPATHIC REM SLEEP BEHAVIOR DISORDER

Most patients with idiopathic REM sleep behavior disorder (IRBD) are diagnosed with the synucleinopathies Parkinson disease (PD) and dementia with Lewy bodies. Conversion rates have been estimated to be 35% at 5 years, 73% at 10 years, and 92% at 14 years after IRBD diagnosis.(1) Accordingly, IRBD is considered as a marker of the prodromal stage of synucleinopathies. In PD, RBD occurs in about 50% of the patients and in 18% of them, RBD symptoms precede the onset of parkinsonism.(2) Most cases of PD are sporadic, but approximately 5% to 10% of cases encompass monogenic forms caused by mutations in PD-associated genes. Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene represent the most common genetic cause of both familial PD and sporadic PD (sPD). Indeed, the G2019S mutation has been detected in up to 6% of familial and 3% of sPD cases in Europeans.(3) Moreover, the LRRK2-associated PD form (LRRK2-PD) is clinical and neuropathologically similar to sPD lacking LRRK2 mutations.(3</SUP)