Chronic rheumatic heart disease is the result of scarring following a childhood episode (or episodes) of acute rheumatic fever, which causes inflammation of the heart. Rheumatic fever is an over-reaction of the immune system following a sore throat (pharyngitis) due to a particular type of bacteria (group A Streptococci). The immune reaction to this infection can cause inflammation of the heart and many other organs, but the damage to the inner lining of the heart (endocardium) is the major problem, because it often results in valvular damage due to healing by scarring. The valvular injury may take many years to become clinically apparent.
Rheumatic fever is largely preventable by eliminating overcrowding (thereby reducing the likelihood of bacterial spread from person to person), improving nutrition (thereby reducing susceptibility to infection), as well as prompt treatment of bacterial sore throats. The incidence of rheumatic fever and chronic rheumatic heart disease has decreased markedly in Australia, except in the indigenous population, who still suffer the world's highest incidence of this disease.