The finding of common mitochondrial dysfunctions, such as altered quality control mechanisms, imbalance in calcium homeostasis, impairment in trafficking in PD as well as in atypical parkinsonism and HD, the involvement of PINK1/Parkin both in PD and HD, and the possibility of producing animal models of all these neurodegenerative diseases by using toxins acting on mitochondrial respiratory chain, suggests that these events are probably important but not the trigger of neurodegeneration. The gene discussed is PRKN; the disease is Huntington disease.