SNCA and Parkinson disease: PD is a progressive neurodegenerative disease marked by motor deficits such as myotonia and resting tremor.583 In addition to the traditionally recognized loss of dopaminergic neurons in the substantia nigra and intracellular alpha-synuclein (α-syn) deposition, the brains of PD patients exhibit iron deposition, heightened oxidative stress, and lipid peroxidation damage.