The chorea of McLeod syndrome

Among the movement disorders associated with acanthocytosis, McLeod syndrom e (McKusick 314850) is the one that is best characterized on the molecular level. Its defining feature is low reactivity of Kell erythrocyte antigens. This is due to absence of membrane protein KX that forms a complex with th e Kell protein. KX is coded for by the XK gene on the X-chromosome. We pres ent six males (aged 29 to 60 years). with proven XK mutations, to discuss t he chorea associated with McLeod syndrome. The movement disorder commonly d evelops in the fifth decade and is progressive. It affects the limbs, the t runk and the face. In addition to facial grimacing, involuntary vocalization can be present. I n early stages there may only be some restlessness or slight involuntary di stal movements of ankles and fingers. Lip-biting and facial tics seem more common in autosomal recessive choreoacanthocytosis linked to chromosome 9. This, together with the absence of dysphagia in McLeod syndrome, may help i n differential diagnosis. Recent findings suggest a role for the endothelin system of the striatum in the pathogenesis of McLeod syndrome. (C) 2001 Mo vement Disorder Society.