[Differential diagnosis of chorea].

Chorea is an involuntary movement that appears along with many diseases, it is commonly described as a frequent, brief, sudden, and twitch-like movement that is manifested in various parts of the body in a chaotic pattern. Huntington disease (HD) is a representative neurodegenerative disorder that presents with chorea. Although HD is caused by a CAG-repeat expansion in the IT-15 gene which encodes huntingtin, a small group of patients showing the symptoms and signs of HD do not have the causative CAG-repeat expansion, thereby showing that autosomal-dominant chorea is genetically heterogeneous. Recent studies have demonstrated that such disorders include dentatorubral pallidoluysian atrophy (DRPLA), spinocerebellar ataxia type 17 (SCA17), Huntington disease like 1 (HDL1), Huntington disease like 2 (HDL2), and benign hereditary chorea (BHC). We recently identified 2 Japanese families with adult-onset benign chorea that was inherited in an autosomal-dominant pattern that was linked to chromosome 8q22.2-q23.3, and we named this disease "benign hereditary chorea type 2 (BHC2)". Chorea can also be caused by a wide range of other hereditary diseases and sporadic disease such as metabolic, infectious, inflammatory, vascular, and drug-induced syndromes. In this article, we have reviewed the clinical features of the disorders associated with chorea.