Rheumatic fever is commonly associated with affection of: September 2005

Ans. B: Mitral valveRheumatic fever is a systemic disease affecting the peri-aeriolar connective tissue and can occur after an untreated Group A Beta hemolytic streptococcal pharyngeal infection.It is believed to be caused by antibody cross-reactivity. This cross-reactivity is a Type II hypersensitivity reaction and is termed molecular mimicry.Group A streptococcus pyogenes has a cell wall composed of branched polymers which sometimes contain M protein that are highly antigenic. The antibodies which the immune system generates against the M protein may cross react with cardiac myofiber protein myosin, hea muscle glycogen and smooth muscle cells of aeries, inducing cytokine release and tissue destruction.