Rheumatic fever is a rare inflammatory illness that can occur after "strep throat," an infection of the throat and tonsils by the bacterium group A Streptococcus (GAS) or Streptococcus pyogenes. Most strep throat strains do not cause rheumatic fever. This disease is currently very rare in the United States and in other developed nations, but is still common in many developing countries due to lack of treatment for strep throat. Rheumatic fever can almost always be prevented if strep throat is properly treated.
Rheumatic fever can affect different parts of the body with varying symptoms, which may include: joint pain and swelling, skin rash, abnormal involuntary movements, and bumps under the skin. It can also permanently damage the heart, leading to rheumatic heart disease.