Glucocerebrosidase gene variants are accumulated in idiopathic REM sleep behavior disorder

Glucocerebrosidase (GBA) gene variants are associated with the development of the Lewy body disorders (LBD) Parkinson disease (PD) and dementia with Lewy bodies (DLB). Idiopathic REM sleep behavior disorder (IRBD) represents prodromal LBD in most instances. We investigated whether GBA variants are overrepresented in IRBD and if their presence shortens the time to conversion to clinically-defined LBD.

All GBA coding exons from 69 polysomnography-confirmed IRBD patients and 84 matched controls were sequenced by the Sanger method.

Seven missense variants (E326K, L444P, A446T, A318G, R329C, T369M, N370S) were identified in eight (11.6%) IRBD patients and in one (1.2%) control (P = 0.026). After a mean follow-up of 8.9 ± 3.8 years from IRBD diagnosis, five subjects with GBA variants developed LBD (3 DLB and 2 PD) and three remained disease-free. The risk of developing a LBD was similar in IRBD subjects with GBA variants than in those without variants (log rank test, p = 0.935).

In IRBD, GBA variants are 1) more frequent when compared to controls, 2) associated with impending PD and DLB but 3) not indicative of a short-term risk for LBD after IRBD diagnosis. IRBD patients carrying GBA variants could be studied with disease-modifying interventions aiming to restore the GBA metabolic pathway.