As almost all cases develop after a streptococcus bacteria throat infection, most experts believe the condition is caused by your immune system malfunctioning.
During a throat infection, the lining of your throat becomes inflamed to prevent the infection from spreading. This is caused by your immune system responding to the infection.
In cases of rheumatic fever, it seems that the process of inflammation goes out of control and spreads throughout your body, including:
- the heart, which causes the symptoms of chest pain, fatigue and shortness of breath,
- the joints, which causes the symptoms of arthritis,
- the skin, which causes the symptoms of the skin rash and nodules, and
- the nervous system, which causes the symptoms of chorea (uncontrollable jerking) and the changes in personality associated with rheumatic fever.
Exactly why the immune system suddenly stops working properly is unclear. One theory is that the streptococcal bacteria have a similar molecular structure to certain tissues in the body. So the immune system may begin by targeting the bacteria and then mistakenly go on to target tissues that share a similar molecular structure.
Another theory is that some people may be born with certain genetic factors that make their immune system more likely to malfunction after a throat infection.
