Hereditary chin tremor in Parkinson's disease.

Hereditary chin tremor (HCT) is characterized by rhythmical, involuntary movements of the chin muscles usually inherited in an autosomal dominant pattern. We describe a 74-year old man with familial, childhood-onset chin tremor, and a 3-year history of progressive hand tremor, gait difficulty, and other parkinsonian features. Since chin tremor often occurs in Parkinson's disease (PD), a coexistent HCT may not be recognized unless past and family history of tremor is carefully explored.