Parkinson's disease (PD), the most common movement disorder, is characterized by age-dependent degeneration of dopaminergic neurons in the substantia nigra of the mid-brain. Non-motor symptoms of PD, however, precede the motor features caused by dysfunction of the dopaminergic system, suggesting that PD is a systemic disorder. Mitochondrial dysfunction has long been observed in PD patients and animal models, but the mechanistic link between mitochondrial dysfunction and PD pathogenesis is not well understood. Recent studies have revealed that genes associated with autosomal recessive forms of PD such as PINK1 and Parkin are directly involved in regulating mitochondrial morphology and maintenance, abnormality of which is also observed in the more common, sporadic forms of PD, although the autosomal recessive PDs lack Lewy-body pathology that is characteristic of sporadic PD. These latest findings suggest that at least some forms of PD can be characterized as a mitochondrial disorder. Whether mitochondrial dysfunction represents a unifying pathogenic mechanism of all PD cases remains a major unresolved question.
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