Sydenham chorea

Sydenham chorea results from molecular mimicry: antibodies raised against group A streptococcal antigens cross-react with epitopes on neurons of the basal ganglia, particularly the caudate and putamen. It is the only Jones major criterion that can appear alone and late, typically one to eight months after the inciting pharyngitis, by which time throat cultures and even ASO titres may have normalized. Children aged five to fifteen are most affected and girls more than boys. Clinically there are darting, purposeless movements, milkmaid's grip (rhythmic squeezing on sustained grasp), darting tongue, motor impersistence, and a striking emotional lability or obsessive-compulsive symptoms; movements disappear in sleep. It is usually self-limited over weeks to months, and treatment is symptomatic with valproate or carbamazepine, with dopamine antagonists reserved for severe cases. Because chorea signals rheumatic fever, these patients require long-term penicillin prophylaxis and echocardiographic assessment for valvular disease, above all mitral stenosis.