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Rheumatic fever and its cardiac sequelae continue to be an enigma as to why some people are predisposed to cardiac involvement while others are not. That this is due in predisposed patients to an autoimmune reaction to untreated or partially treated group A streptococcal pharyngitis has been established. The component of the bacteria responsible for the antigen cross reactivity to the heart tissue has not been established. Cross reactivity was initially observed in extracts of the streptococcal cell wall. The M protein has been the most extensively studied component of the streptococcus.1 The streptococcal cell wall has a high concentration of N-acetyl-glucosamine, which is also found in high concentrations in valvar tissue.2
The group A streptococcus capsule is composed of hyaluronic acid, which is also increased in valves having increased myxomatous tissue.3 As hyaluronic acid is a common component we hypothesised that this may be responsible for the cross reactivity.
We studied 134 mitral and aortic valves removed surgically for either stenosis or regurgitation or from double valve replacements. The valves were examined grossly for commissural fusion; thickening of leaflets; shortening, thickening and fusion of chordae tendineae; and presence of calcification. …