|Healed Rheumatic Mitral Valvulitis with Stenosis|
Unknown. However, there is abundant epidemiological evidence that attacks are preceded by streptococcal infections.
Immunologic hypothesis is that related antigens found in myocardium and streptococci result in cross reactions of anti-strep. antibodies with cardiac tissues, or that some other immunologic mechanism is initiated by streptococcal antigens.
Unknown. Abundant evidence for immune mechanisms.
Potential cross reactive components of cardiac tissues and streptococci: valvular glycoproteins and strep. hyaluronate capsule; myocardial muscle sarcolemma and strep. membranes; cardiac myosin and strep. M protein, the chief virulence factor of Group A streptococci.,
Acute attacks occur mostly between 5-15 years of age. following a streptococcal pharyngitis.
Incidence has decreased in the USA over the past 50 years, from a death rate of about 20 to 2 per 100,000.
Incidence still high worldwide. Clear that low incidence here not entirely due to preventive measures, but more to variable virulence of prevailing strains.
Outbreaks in the 80's in Utah, Ohio, Pennsylvania, and two armed forces bases led to recovery of Strep. strains M3 and M18, the prevailing strains of the 40's.
|General Gross Description|
Acute Phase: A pancarditis visible grossly in valves and pericardium. Valves show evenly spaced small 1-2mm verrucae along lines of valve closure adjacent to edges. Pericardium shows a grossly non-specific fibrinous pericarditis similar to what may be seen in uremia or in an acute myocardial infarct.
Chronic Phase: Valve deformities include thickening of leaflets and chordae tendinae with fusion of commissures causing stenosis and regurgitation. Characteristic mitral stenosis causes hypertrophy and dilatation of left atrium with atrophy of left ventricle. Aortic stenosis causes left ventricular hypertrophy. A dominant mitral regurgitation causes dilatation and hypertrophy of all 4 chambers.
|General Microscopic Description|
Acute Phase: Aschoff body in myocardium is considered one of the rare truly pathognomonic lesions in pathology.
Consists of a spindle shaped interstitial aggregate of characteristic large mononuclear cells, the Aschoff body, with prominent nuclei and cytoplasm often arranged in curious parallel rows separated by a fibrinoid exudate, considered to be a fibrinoid necrosis of collagen and, possibly, myocardial fibers.
Valvular lesions show a surface fibrinoid necrosis with an underlying continuous exudate of large reactive cells like those seen in an Aschoff body.
Chronic Phase: Scars replace the destroyed tissues, and are non-specific in appearence. Hemodynamic injury to deformed valves increases tendency to further fibrosis and calcification.
Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 547-60
Harrison's Principles of Internal Medicine, 13th Ed: Isselbach et. al. (eds). New York, McGraw-Hill, 1994, pp. 1046-52.
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|Healed Rheumatic Mitral Valvulitis with Stenosis
||Synopsis by: J. Hasson, M.D. (T38000D72080)