Rheumatic fever. DR : Gehan Mohammed. Learning objectives. Understand the pathogenesis of rheumatic fever. Discuss the Effects of Rheumatic Fever on the three layers of Heart( endocardium,myocardium,pericardium ).
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DR : Gehan Mohammed
Differentiate rheumatic endocarditis from other causes of endocarditis(Nonbacterial Thrombotic EndocarditisNBTE,Infective Endocarditis)
Johnes Major criteria of rheumatic fever
Inflamed joints , self limited, become normal within 1-3 days even without treatments so no chronic deformities.
Major criteria of rheumatic fever
It affects all the 3 layers of the heart;
1- Endocarditis — vegetations due to edema, and fibrin deposits on valve leaflets along lines of closure. Mostly mitral and aortic valve.
Small vegetations (verrucae) are visible along the line of closure of the mitral valve leaflet (arrowheads). Previous episodes of rheumatic valvulitis have caused fibrous thickening and fusion of the tendinous cords.
Microscopic appearance of an Aschoff body in a patient with acute rheumatic carditis. The myocardial interstitium has a circumscribed collection of mononuclear inflammatory cells, including some large histiocytes with prominent nucleoli, a prominent binuclear histiocyte, and central necrosis.
3- Pericarditis — "bread and butter appearance", due to fibrinous inflammation and deposition of fibrin on surface of pericardium.
Manifests years or decades after the initial episode of rheumatic fever.
The distribution of valve involvement is variable:
a- stenosis (Reduction of diameter): fish mouth (button hole) stenosis
b- regurgitation (improper closure) : if fibrosis occurred in chordae tendonae so leaflets are retracted.
Diffferential diagnosis for rheumatic Endocarditis
Less common, occur in patients with systemic lupus erythematosus due to deposition of circulating immune complexes in the valves.
a- obstruct valve orifice
b- lead to rupture of the leaflets, cordaetendineae, or papillary muscles
c- abscess in perivalvular tissue (ring abscess) friable large yellow vegetations may become systemic emboli infarcts + abscesses.
Histologic appearance of vegetation of endocarditis with extensive acute inflammatory cells and fibrin. Bacterial organisms were demonstrated by tissue Gram stain.
1- rheumatic heart disease: vegetations are marked by a row of warty, small vegetations along the lines of closure of the valve leaflets.
2- IE (infective endocarditis): vegetations are characterized by large, irregular masses on the valve cusps that can extend onto the cords .
3- NBTE (nonbacterial thrombotic endocarditis) typically exhibits medium sized bland vegetations, usually attached at the line of closure.
4-LSE (Libman-Sacks endocarditis) has small or medium-sized vegetations on either or both sides of the valve leaflets.