PINK1 and Parkinson disease: While it is important to note that the limited availability of autopsy cases may cause an underestimation of the pathological heterogeneity of PRKN and PINK1 PD, the combined clinical-pathological evidence of highly selective SNpc DA neuron loss suggests that these genes may represent an Achilles heel of SNpc DA neurons and that studying downstream pathological pathways may be critical for yielding insights into the vulnerability of the population in PD.