Sydenham's Chorea: Causes and symptoms

The cause is only certain types of streptococci, called "Lancefield Group A beta-hemolytic." These particular germs seem to be able to create an immune response that attacks the body's own tissues along with the germs. Those tissues are joints, heart valves, skin, and brain.

Many patients suffer from strep throat, just before developing this new set of symptoms. They may also have joint pains without swelling, a condition known as arthralgia. Sydenham's chorea will appear as uncontrollable twitching or jerking of any part of the body that is worse when trying to repress it but disappears with sleep.

— J. Ricker Polsdorfer, MD