Parkinson disease 4, autosomal dominant is a complex neurodegenerative disorder that can present with a range of symptoms from typical Parkinson disease to dementia with Lewy bodies. Clinical features include parkinsonian symptoms like resting tremor, rigidity, postural instability, and bradykinesia, as well as dementia, diffuse Lewy body pathology, autonomic dysfunction, hallucinations, and paranoia. This disease is associated with a late onset and is caused by a heterozygous triplication of the alpha-synuclein gene on chromosome 4q22.