A neurodegenerative disorder characterized by parkinsonian signs such as rigidity, resting tremor and bradykinesia. A subset of patients manifest additional symptoms including hyperreflexia, autonomic instability, dementia and psychiatric disturbances. Symptoms show diurnal fluctuation and can improve after sleep. The disease is Experimental Factor Ontology entry EFO_0022988 (Parkinson disease 6). Also known as: PARK6.