Familial PD cases have been related with mutations, duplications and triplications in SNCA (α-synuclein)/PARK1, parkin/PARK2, UCHL-1 (ubiquitin carboxy-terminal hydrolase L1)/PARK5, DJ-1/PARK7, PINK-1 (PTEN-induced putative kinase)/PARK6, LRRK2/PARK8, ATP13A2 (p-type ATPase)/PARK9, and HTRA2 (HtrA serine peptidase 2)/PARK13. The gene discussed is HTRA2; the disease is Parkinson disease.