HTRA2 and Parkinson disease: Later on, replications with contradictory consequences have been conducted [25–31], and one large scale genetic association study is worth noting, which showed no evidence for an overall association of common variants in HTRA2 with PD [32], while Gulsuner et al.'s study of a six-generation family provides further evidence for the probability of HTRA2 acting as a cause for PD and ET, especially those with family history [13].