A form of Parkinson disease (PD) characterized by an age of onset between 21-45 years, rigidity, painful cramps followed by tremor, bradykinesia, dystonia, gait complaints and falls, and other non-motor symptoms. A slow disease progression and a more pronounced response to dopaminergic therapy are also observed in most YOPD forms. The disease is young-onset Parkinson disease (Monarch Disease Ontology term MONDO_0017279). Also known as: YOPD, early-onset Parkinson disease.