Although most cases are sporadic, several mutations have been described in familial and early-onset forms of PD, such as mutations in PARK1 (encoding PINK1), PARK2 (encoding for Parkin), PARK1/4 (α-synuclein), PARK7 (DJ1), PARK8 (LRRK2), PARK9 (ATP13A2) PARK17 (Vsp35), FBX07, GIGYF2, or HTRA2, highlighting the involvement of the ubiquitin protein degradation pathway, oxidative stress, cell survival pathway, mitochondrial function, and apoptosis in PD pathogenesis [113,318]. This evidence concerns the gene HTRA2 and Parkinson disease.