Rheumatic Fever



Pathophysiology of Rheumatic fever

rheumatic fever is

1) caused by group A beta-hemolytic streptococci infection
2) this organism produces anti-M protein antibodies, which cross-react with human heart tissue 3) most important long-term sequelae is cardiac valve disease (both stenosis and regurgitation)

Signs and Symptoms

1) diagnosis is by presence of two major criteria or one major and two minor criteria plus evidence of antecedent infection with group A strep.

Major criteria of Β rheumatic fever

2) carditis
3) migratory polyarthritis (usually in large joints such as ankles, knees, wrists, and elbows)
4) chorea
5) erythema marginatum
6) subcutaneous nodules over extensor surfaces of joints

Minor criteria of rheumatic fever

7) fever
8) arthralgia
9) increased acute phase reactants

Characteristic Test Findings

Laboratory -

1) increased antistreptolysin O titers (80%)
2) positive throat culture for Strep (25%)

EKG -

3) prolonged PR interval
4) S3 gallop

Histology/Gross Pathology

1) causes pancarditis (endocardium, myocardium, pericardium all involved)
2) commissural fusion of aortic and mitral valves
3) lymphocytic infiltrate with fibrinoid degeneration and Aschoff’s bodies in myocardium

Associated Conditions

1) usually follows a pharyngitis
2) affects mitral valve most commonly followed by aortic valve
3) can be reactivated by recurrent streptococcal infection
4) pericardial friction rub and cardiomegaly

Biochemistry

group A streptococcal antibodies found in rheumatic fever:

1) antistreptolysin O
2) anti-deoxyribonuclease
3) antihyaluronidase B

Inheritance/Epidemiology

1) acute rheumatic fever is most common in children ages 5-15 yers
2) 3% of untreated group A Strep pharyngitis patients develop rheumatic fever
3) causes tricuspid stenosis in women in tropical and subtropical cases

Treatment

1) oral penicillin V 500 mg BID or erythromycin 250 mg QID or 1.2 million units penicillin G IM as initial therapy
2) lower dose for up to 5 years for prevention of recurrent disease
3) salicyclates for 4-6 weeks
4) avoidance of vigorous activity in acute phase

Tips for USMLE

1) think of a previous episode of rheumatic fever if a 56 year old woman had a “bad Strep infection” in her teenage years and now has both aortic and mitral stenosis
2) if a patient has aortic stenosis from rheumatic fever, the mitral valve is almost always involved also.

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