Rheumatic fever can affect the heart, joints, skin and other organs.
Children between the ages of 5 and 15 are most susceptible to this condition. Rheumatic fever is caused when the body's immune system makes antibodies to fight the strep bacteria that cause an infection. Certain parts of the bacteria are similar to some kinds of human tissues. These antibodies become confused and begin to target tissues in the body. Rheumatic fever is rare.