Currently, the yield of genetic testing in PD in most settings is ∼5%–15%, depending on the population studied and the platform used (most commonly targeted gene panels or single-gene studies).11, -, 13 However, this has been shown to be as high as 40%–50% in some populations.3,14, -, 17 Known PD/parkinsonism genes have an autosomal dominant (e.g., SNCA, LRRK2, and VPS35), autosomal recessive (e.g., PRKN, PINK1, and PARK7/DJ-1) or X-linked (TAF1) mode of inheritance. This evidence concerns the gene SNCA and Parkinson disease.