The disease occurs in genetically predisposed individuals as a consequence of an abnormal response of the body's defense system (immune system) to throat infections caused by Streptococcus. In these subjects the immune response not only fights infection but also attacks the body itself. So, between the infection and the onset of symptoms takes place a variable time span.
The relationship of the disease with a previous infection is the basis of treatment and prevention. Strep throat is common in the general population, although only a small minority of subjects develop the disease. The risk increases in patients with a history of prior Rheumatic Fever, especially in the 3 months following the diagnosis.