The above picture shows the presence of Aschoff bodies, which are pathognomic for Rheumatic Hea Disease. Rheumatic fever (RF) is an acute, immunologically mediated, multisystem inflammatory disease classically occurring a few weeks after an episode of group A streptococcal pharyngitis; occasionally, RF can follow streptococcal infections at other sites, such as the skin. Acute rheumatic carditis is a common manifestation of active RF and may progress over time to chronic rheumatic hea disease (RHD), mainly manifesting as valvular abnormalities. RHD is characterized principally by deforming fibrotic valvular disease, paicularly involving the mitral valve; indeed, RHD is viually the only cause of mitral stenosis Type of necrosis seen in RHD - Fibrinoid necrosis. Morphology: Distinctive lesions occur in the hea, called Aschoff bodies, consisting of foci of T lymphocytes, occasional plasma cells, and plump activated macrophages called Anitschkow cell (pathognomonic fo RF).These macrophages have abundant cytoplasm and central round-to-ovoid nuclei (occasionally binucleate) in which the chromatin condenses into a central, slender, wavy ribbon (hence the designation "caterpillar cells").