The carditis/cardiomyopathy of rheumatic fever: relationship to pathogenesis.

Although the relationship between group A streptococcal upper respiratory tract infection and the development of acute rheumatic fever has been known for many years, the pathogenetic mechanism(s) have never been defined. Thus, the mechanism of damage to the valves and to the myocardium in patients with rheumatic fever remains unexplained. Traditionally, emphasis has been placed on the valvular damage in rheumatic heart disease, but there is considerable evidence for myocardial involvement. An abnormal immune response to some as yet unrecognized somatic or extracellular antigen of the group A streptococcus is probably related to the cardiomyopathy. This abnormal immune response is supported by considerable clinical and experimental evidence. Recent studies have suggested other mechanism to explain the myocardial damage including the influx of lymphocytes into the area as well as the possibility of damage relating to generation of oxygen-free radicals. As more sophisticated molecular biological studies of the group A streptococcus become available, perhaps the mystery of this very unique and common cardiomyopathy can be resolved.