Causes
Rheumatic fever is caused by a combination of bacterial infection and immune system overreaction. It almost always follows a strep throat infection, which is an infection of the respiratory tract caused by bacteria of the Streptococcus family. Children are far more likely to get strep throat than adults.
Normally, Streptococcus causes a cough and a sore throat, and clears up with antibiotics. In some cases, however, children with strep throat begin complaining of pain in the joints or other unusual symptoms. This usually happens 2 to 4 weeks after the streptococcal infection (which may have already cleared up).
The disease has an affinity for the joints, the central nervous system (brain and spinal cord), and the heart. In the heart, the disease can affect the inner lining of the heart including the heart valves (endocarditis), the muscle of the hear (myocarditis), or the covering of the heart (pericarditis).
In some people, the body reacts with a massive immune system reaction to the affected areas. The cells that normally kill invading bacteria become so active that they also attack the affected tissues. The result in the joints is temporary arthritis (inflammation of the joints). In the heart, they can permanently damage heart valves, increasing the risk of heart problems later in life. Rheumatic fever can also cause problems with the nervous system that are usually reversible.