Rheumatic fever, health and medicine homework help

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what are the diagnostic features of rheumatic fever

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RHEUMATIC FEVER
Definition
 Rheumatic fever is an inflammatory disease that follows infection with certain strains of
group A streptococci.
 Acute rheumatic fever (ARF) is a delayed, nonsuppurative sequela of a pharyngeal infection
with the group A streptococcus (GAS).
 Following the initial pharyngitis, a latent period of two to three weeks occurs before the first
signs or symptoms of ARF appear
 The disease presents with various manifestations that may include arthritis, carditis, chorea,
subcutaneous nodules, and erythema marginatum.
 The disease affects the heart, joints, central nervous system, and subcutaneous tissue.
Epidemiology
 Worldwide, there are 470,000 new cases of rheumatic fever and 233,000 deaths attributable
to rheumatic fever or rheumatic heart disease each year; most occur in developing countries
 Among indigenous groups and developing nations, over 15 million people are estimated to
have rheumatic heart disease.
 In the United States and other developed countries, the incidence of ARF is much lower at 2 to
14 cases per 100,000; this is probably due to improved hygienic standards and routine use of
antibiotics for acute pharyngitis
 The observation in some studies that only a few M serotypes (types 3, 5, 6, 14, 18, 19, 24, and
29) were implicated in outbreaks of rheumatic fever in the United States suggested a
particular "rheumatogenic" potential of certain strains of GAS
Etiology
 Epidemiologic studies suggest an individual propensity to develop rheumatic fever, a
nonsuppurative complication of group A streptococcal infection of the upper respiratory
tract must occur, which occurs most commonly in children 5 to 15 years of age.
 Streptococcus pyogenes (-hemolysis group A streptococci) cause both superficial
infections (e.g. pharyngitis, impetigo) and invasive diseases.
 Rheumatic fever occurs in 3% of patients who carry an infecting strain for more than 3
weeks after convalescence, whereas persons carrying the organism for less than 3 weeks
have an incidence of only 0.3%.
 Patients with streptococcal infections and a history of previous rheumatic fever have a 5 to
50% greater incidence of rheumatic fever than do patients with no prior history of the
disease; this tendency declines with age.

 Environmental factors (latitude, altitude, humidity), nutrition, crowding, and age appear to
influence the incidence of rheumatic fever, probably because the same factors influence the
incidence of streptococcal infection.
 Pathologic changes are found throughout the body in connective tissue and around small
blood vessels.
 The pathognomonic lesion of rheumatic fever is the Aschoff body, an inflammatory lesion
associated with swelling and fragmentation of collagen fibers and alterations in the staining
characteristics of connective tissue.
 Endocarditis produces a verrucous valvitis that may heal with fibrous thickening and
adhesions of valve commissures and chordae tendineae, resulting in variable degrees of
valve stenosis and insufficiency.
 The mitral and aortic valves are affected most commonly, the tricuspid less frequently, and
the pulmonary valve rarely.
 Pathologic changes in the joints consist of exudation with edema of synovial membranes,
focal necrosis in the joint capsule, edema and inflammation in periarticular tissue, and joint
effusion.
 Subcutaneous nodules seen during the acute phase of the disease resemble Aschoff bodies
and are granulomas with localized areas of fibrinoid swelling of collagen and perivascular
infiltration with large cells, pale nuclei, and prominent nucleoli.
 "Rheumatic pneumonia" consists of exudative and inflammatory changes without Aschoff
bodies.
Pathogenesis
 The pathogenic mechanisms that lead to the development of acute rheumatic fever remain
incompletely understood.
 Clearly streptococcal pharyngeal infection is required, and genetic susceptibility may be
present.
 On the other hand, evidence is sparse that toxins produced by the streptococcus are
important.
 Within this framework, molecular mimicry is thought to play an...


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