Parkinson’s disease (PD) is one of the most common neurodegenerative diseases, and the role of ?-synuclein accumulation and the subsequent death of dopaminergic neurons in the midbrain have long been recognized as key steps in the disease. Progress in understanding genetic risk factors, meanwhile, has uncovered multiple genetic risk factors. Even though aging is the single biggest risk factor for PD, there are versions of the disorder that affect children.