This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Rheumatic fever is commonly associated with affection of: September 2005 
Select and explain. 
A. Tricuspid valve, B. Mitral valve, C. Aoic valve, D. Pulmonary valve
B: Mitral valve
Answer: B: Mitral valve 
Explanation: 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.