The Remote Assessment of Parkinsonism Supporting Ongoing Development of Interventions in Gaucher Disease – Study Protocol

Abstract Mutations in GBA which are causative of Gaucher disease in their biallelic form, are the most common genetic risk factor for Parkinson disease. The diagnosis of Parkinson disease relies upon clinically defined motor features which appear after irreversible neurodegeneration. Prodromal symptoms of Parkinson disease may provide a means to predict latent pathology, years before the onset of motor features. Previous work has reported prodromal features of Parkinson disease in GBA mutation carriers, however this has been insufficiently sensitive to identify those that will develop Parkinson disease. The Remote Assessment of Parkinsonism Supporting Ongoing Development of Interventions in Gaucher Disease (RAPSODI) study assesses a large cohort of GBA mutation carriers, to aid development of procedures for earlier diagnosis of Parkinson disease. Summary Points The therapeutic focus for Parkinson disease is currently symptomatic, rather than disease-modifying or neuroprotective. Non-motor prodromal features of Parkinson disease may precede the motor symptoms required for clinical diagnosis by several years. GBA mutations, which are associated with Gaucher disease in their biallelic form, have emerged as the most common genetic risk factor for Parkinson Disease. GBA associated PD displays a slightly exaggerated phenotype, including earlier age of onset, enhanced cognitive decline, more severe affective disturbances, and a greater likelihood of manifesting REM Sleep Behaviour Disorder, hyposmia and autonomic dysfunction. The RAPSODI GD study is an annual remote assessment which aims to define the clinical prodrome of PD in a large cohort of GBA mutation carriers, to accurately predict clinical diagnosis. The secondary objectives of RAPSODI GD are to risk stratify homozygote and heterozygote GBA mutation carriers for PD risk, understand the variable penetrance of the GBA associated PD phenotype, and create a platform for the future evaluation of biomarkers of disease. The putative implication of the RAPSODI GD study is to contribute towards earlier diagnosis of GBA associated PD, to provide a timeframe for delivering neuroprotective interventions. Defining prodromal PD in GBA carriers may have wider implications for sporadic PD.