Sydenham chorea (SC), also known as St. Vitus dance, St. Johannis' chorea, chorea minor, or rheumatic chorea, is one of the major clinical manifestations of acute rheumatic fever (ARF) and is the most common form of acquired chorea in childhood. It is a movement disorder characterized by chorea (involuntary brief, random and irregular movements of the limbs and face), emotional lability, and hypotonia.
The incidence of ARF and SC has declined dramatically in the Western world . However, chorea is still a common manifestation of rheumatic fever, particularly in developing countries. In the United States, chorea was reported in 18 to 36 percent of cases of rheumatic fever [2-5]. Chorea also may occur as the initial manifestation of other illnesses, particularly systemic lupus erythematosus .
Other clinical manifestations of ARF and the approach to diagnosis of rheumatic fever are presented separately. (See "Clinical manifestations and diagnosis of acute rheumatic fever".)
Although SC clearly is related to group A streptococcal infection , its pathogenesis is not completely understood. Molecular mimicry, in which antibodies directed against part of the group A streptococcus bacterium crossreact with host antigens in susceptible subjects, is thought to play an important role.
In acute rheumatic fever, antibodies are mounted against N-acetyl-beta-D-glucosamine (NABG or GlcNAc), the immunodominant carbohydrate antigen of group A streptococci. These antibodies likely play a role in valvular injury in rheumatic carditis, and in other manifestations of ARF (see "Epidemiology and pathogenesis of acute rheumatic fever", section on 'Molecular mimicry'). Different subsets of NABG antibodies appear to correlate with distinct clinical manifestations of ARF. In Sydenham chorea, the antibodies bind to lysoganglioside on the neuronal cell surface [8,9], where they are capable of triggering a signaling cascade . These antibodies also recognize the intracellular protein tubulin . Tubulin-specific antibodies are not found in patients with acute rheumatic fever without SC, or in patients who have recovered from SC. The genes encoding these antibodies are similar to the genes encoding antibodies implicated in the pathogenesis of motor neuropathies . Thus, tubulin appears to be an important neuronal target in the pathogenesis of Sydenham chorea.