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Incidence & Etiology

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Acute rheumatic fever is a multisystem disease that occurs as a complication of streptococcal pharyngitis (Figure 22-1). It occurs mainly in children between 5 and 15 years of age, particularly those with low socioeconomic backgrounds who live in the overcrowded conditions that favor streptococcal pharyngitis. It is still prevalent in developing countries. Although its incidence has decreased in the United States, it occurs during sporadic epidemics of streptococcal pharyngitis. During such epidemics, approximately 3% of patients develop acute rheumatic fever.

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Figure 22–1.
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The temporal relationship between streptococcal infection and acute rheumatic fever.

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Streptococcal pharyngitis caused by specific M serotypes of group A streptococci have a higher incidence of acute rheumatic fever than others. These are associated with the presence of high virulence factors such as (1) a high concentration of surface M protein—M types 5, 19, 24; and (2) large hyaluronate capsules (which produce mucoid colonies on culture)—M types 3 and 18. These serotypes are commonly responsible for epidemic streptococcal disease in the United States.

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No genetic susceptibility factors have been identified.

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Pathogenesis

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The exact relationship between streptococcal infection and acute rheumatic fever is unknown. Cardiac injury is not the direct result of infection as shown by negative streptococcal cultures in affected heart tissue. The following facts suggest that the relationship is the result of an unproved immunologic hypersensitivity to streptococcal antigens: (1) Acute rheumatic fever occurs 2–3 weeks after streptococcal pharyngitis, often after the patient has recovered from the pharyngitis (Figure 22-1). (2) High levels of antistreptococcal antibodies (antistreptolysin O, anti-deoxyribonuclease (DNase), antihyaluronidase) are present in patients who develop acute rheumatic fever. (3) Early treatment of streptococcal pharyngitis with penicillin decreases the risk of acute rheumatic fever. (4) Immunoglobulin and complement are present on the surface membrane of affected myocardial cells.

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While immunologic hypersensitivity is likely, the mechanism remains unknown. The presence of antibodies with activity against both streptococcal antigens and myocardial cells suggests the possibility of a type II hypersensitivity mediated by crossreacting antibodies. The presence in the serum of some patients of immune complexes formed against streptococcal antigens suggests type III hypersensitivity.

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Clinical Features

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Table Graphic Jump Location
Table 22–1. Clinical Features for Diagnosis of Rheumatic Fever (Jones Criteria). 1

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