High Quality Content by WIKIPEDIA articles! Rheumatic fever is an inflammatory disease that may develop two to three weeks after a Group A streptococcal infection (such as strep throat or scarlet fever). It is believed to be caused by antibody cross-reactivity and can involve the heart, joints, skin, and brain[1]. Acute rheumatic fever commonly appears in children between ages 5 and 15, with only 20% of first time attacks occurring in adults.