Abstract OBJECTIVE To discover genetic determinants of Parkinson disease (PD) motor subtypes, including Tremor Dominant (TD) and Postural Instability/Gait Difficulty (PIGD) forms. METHODS In 3,212 PD cases of European ancestry, we performed a genome-wide association study (GWAS) examining two complementary outcome traits derived from the Unified Parkinson’s Disease Rating Scale (UPDRS), including dichotomous motor subtype (TD vs. PIGD) or a continuous tremor / PIGD score ratio. Logistic or linear regression models were adjusted for sex, age of onset, disease duration, and 5 ancestry principal components, followed by meta-analysis. RESULTS Among 71 established PD risk variants, we detected multiple suggestive associations with PD motor subtype, including GPNMB ( rs199347 , p subtype = 0.01, p ratio = 0.03), SH3GL2 ( rs10756907 , p subtype = 0.02, p ratio = 0.01), HIP1R ( rs10847864 , p subtype = 0.02), RIT2 ( rs12456492 , p subtype = 0.02), and FBRSL1 ( rs11610045 , p subtype = 0.02). A PD genetic risk score integrating all 71 PD risk variants was also associated with subtype ratio (p = 0.026, ß = −0.04, 95% CI = −0.07, 0). Based on top results of our GWAS, we identify a novel suggestive association at the STK32B locus (rs2301857, p ratio = 6.6×10 −7 ), which harbors an independent risk allele for essential tremor. CONCLUSIONS Multiple PD risk alleles may also modify clinical manifestations to influence PD motor subtype. The discovery of a novel variant at STK32B suggests a possible overlap between genetic risk for essential tremor and tremor-dominant PD.

Genome-Wide Association Study Meta-Analysis for Parkinson’s Disease Motor Subtypes