STEPTRACKERCARDIOVASCULAR | PATHOLOGY + MICROBIOLOGY | HIGH-YIELD REVIEW

Rheumatic Fever & Endocarditis

Immune cross-reaction after strep throat, infection of the valves, and the sterile vegetations that mimic it.

FOCUS ON
Rheumatic fever: weeks after group A strep pharyngitis; molecular mimicry; Aschoff bodies; acute MR, then chronic mitral stenosis. Infective endocarditis: match the organism to the setting (IV drugs → S aureus, dental work → viridans strep, S gallolyticus → colon cancer) and know the peripheral signs.
TOPIC
DETAIL
MECHANISM
CLUE
Acute rheumatic fever
Children 5–15, 2–4 weeks after group A strep pharyngitis (not skin infection).
Antibodies to M protein cross-react with heart, joint, brain and skin antigens (type II)
Jones major criteria: carditis, migratory large-joint arthritis, Sydenham chorea, erythema marginatum, subcutaneous nodules · ↑ ASO / anti-DNase B
Rheumatic carditis
Pancarditis: endocarditis (acute MR, small vegetations on closure lines), myocarditis, fibrinous pericarditis.
Aschoff bodies (granulomas with fibrinoid necrosis); Anitschkow "caterpillar" cells
Myocarditis → HF is the main cause of acute death
Chronic rheumatic heart disease
Repeated attacks scar valves: mitral (almost always) > aortic.
Commissural fusion, thick fused chordae → "fish-mouth" stenosis
Mitral stenosis decades later · penicillin for strep throat prevents it; long-term prophylaxis after RF
Acute infective endocarditis
S aureus: virulent, normal valves, rapid course, large destructive vegetations.
IV drug use → tricuspid valve; septic lung emboli
High fever, new murmur, abscesses
Subacute infective endocarditis
Viridans streptococci on previously damaged valves after dental procedures.
Dextran helps them stick to fibrin-platelet nidus
Insidious fever, weight loss, smaller vegetations
Other organisms
S epidermidis (prosthetic valve), Enterococcus (GU/GI procedures), S gallolyticus (colon cancer), Candida (IVDU, lines), HACEK/Coxiella/Bartonella (culture-negative).
Setting predicts the bug
S gallolyticus → colonoscopy
Peripheral signs
Fever (most common), new murmur, splinter hemorrhages, Janeway lesions (painless palms/soles), Osler nodes (painful finger pads), Roth spots (retina), anemia, splenomegaly.
Janeway = septic microemboli · Osler, Roth, GN = immune complexes
Duke criteria: ≥ 3 blood cultures + echo (TEE)
Complications
Valve destruction → HF; emboli (brain, spleen, kidney; lung if right-sided); mycotic aneurysm; GN; abscess of valve ring.
Vegetation fragments and immune complexes
Conduction block → valve-ring abscess
Sterile vegetations
Marantic (nonbacterial thrombotic) endocarditis in hypercoagulable cancer; Libman-Sacks in SLE (both sides of mitral leaflets).
Platelet-fibrin deposits, no organisms
Emboli without infection

Mechanism — two routes to valve damage

Strep pharyngitis
→
Anti-M protein immunityMolecular mimicry
→
PancarditisAschoff bodies
→
Repeated attacksFibrotic mitral stenosis
Endothelial damageSterile nidus
→
BacteremiaTeeth, needles, lines
→
Infected vegetation
→
Destruction · emboli · immune complexes

Endocarditis organisms by setting

ORGANISM
SETTING
FEATURE
S aureus
IV drugs, normal valve
Acute, tricuspid, septic emboli
Viridans strep
Dental work, damaged valve
Subacute
S epidermidis
Prosthetic valve, early
Biofilm
S gallolyticus
Older adult
Colon cancer link
Enterococcus
GU/GI procedures
Older men
HACEK, Coxiella, Bartonella
Culture-negative
Coxiella: farm animals
Candida
IV drugs, central lines
Large vegetations

How it's tested

COMMON CONFUSIONAcute rheumatic fever causes mitral regurgitation. Chronic rheumatic heart disease, years later, causes mitral stenosis.
THE TRAPEndocarditis due to S gallolyticus (bovis) needs a colonoscopy even after cure. The bacteremia often comes from an unrecognized colon cancer.
YOUR APPROACHRecent strep throat → immune (RF). Bacteremia source → organism → valve side → embolic or immune signs.

If you see… think…

Fever, migratory arthritis and chorea 3 weeks after sore throat → acute rheumatic fever
Granulomas with Anitschkow cells in the myocardium → Aschoff bodies
Fish-mouth mitral valve with fused commissures → chronic rheumatic heart disease
IV drug user, tricuspid vegetation, cavitary lung nodules → S aureus
Subacute endocarditis after a dental extraction → viridans streptococci
S gallolyticus endocarditis → colon cancer — colonoscopy
Painless palm macules → Janeway; painful finger nodules → Osler
Retinal hemorrhage with a pale center → Roth spot
Pancreatic cancer + sterile vegetations + strokes → marantic endocarditis
Culture-negative endocarditis in a farmer → Coxiella burnetii