Parkinson disease 1, autosomal dominant is a neurodegenerative disorder characterized by bradykinesia, resting tremor, muscular rigidity, and postural instability. Additional features include characteristic postural abnormalities, dysautonomia, dystonic cramps, and dementia. The disease involves the loss of dopaminergic neurons in the substantia nigra and the presence of Lewy bodies in various brain areas. It typically manifests after age 50, but early-onset cases are known. The majority of cases are sporadic, with a multifactorial etiology involving environmental and genetic factors. Some patients have a positive family history, with familial forms starting at earlier ages and having atypical clinical features. The disease is linked to a mutation in the alpha-synuclein gene on chromosome 4q22.1.