PGLYRP4 and Parkinson disease: Importantly, we report robust significant associations between PGLYRP4 and disease risk in two independent PD cohorts, and a novel association between PGLYRP4 and age of symptom onset in an Australian PD cohort, as well as interactive risk-modifying effects of polymorphisms in the PGLYRP2, PGLRYP4, and TLR2 genes.