Acute rheumatic fever is a multisystem inflammatory disease that can follow group A streptococcal pharyngitis. The hea is a primary target of this disease and may be damaged sufficiently to develop permanent sequelae. The most impoant of these sequelae is chronic rheumatic hea disease with valvular damage. The damage most often involves the mitral and/or aoic valves. The resulting thickened, blunted cardiac valve leaflets, often with fibrous bridging between valve leaflets and calcification, frequently take on a "fish mouth" or "button hole" stenotic morphology.Good to know:Associate ballooning of valve leaflets with mitral valve prolapse.Associate irregular, bead like calcifications on the annulus with calcification of the mitral annulus, seen in elderly individuals.Associate large vegetations and leaflet perforation with acute bacterial endocarditis, which usually involves healthy, rather than previously damaged, valves. Ref: Carapetis J.R. (2012). Chapter 322. Acute Rheumatic Fever. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.