Pediatric Examination and Board Review by Robert Daum, Jason Canel Read Free Book Online

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    ANSWERS
     
    1. (A) The most common cause of this constellation of symptoms is acute rheumatic fever, a multisystem inflammatory disease. The disease occurs among children 5 to 15 years of age with a peak incidence at 8 years and is rarely seen in children younger than 2 years of age.
    2. (A) Acute rheumatic fever is triggered by group A beta-hemolytic streptococcal infection of the upper respiratory tract. Acute rheumatic fever does not occur following streptococcal skin infections, staphylococcal infections, or enterococcal infections. The pathogenesis of rheumatic fever is thought to be secondary to an immune response to antigens in the M protein of the capsule of the group A beta-hemolytic streptococcus, which occurs in susceptible hosts and cross-reacts with similar epitopes in human joint tissue, heart, and brain tissue. Pathologic findings include inflammatory lesions that include perivascular granulomas consisting of infiltrates of cells and fibrin that are also known as Aschoff bodies.
    3. (B) The incidence of acute rheumatic fever is approximately 0.3-3% in untreated patients with Streptococcus pyogenes pharyngitis. The onset of disease occurs 1-5 weeks later with a mean of 18 days following the onset of pharyngitis. The typical course includes pharyngitis with improvement of symptoms. Two weeks later the patient begins to develop a low-grade fever and the inflammatory response of rheumatic fever.
    4. (A)
    5. (D) Although there is no specific diagnostic laboratory test for rheumatic fever, the diagnosis is based on the Jones criteria. These are separated into major and minor manifestations. Major criteria include polyarthritis, carditis, erythema marginatum, subcutaneous nodules, and chorea. The most common manifestation is polyarthritis occurring in up to 70% of patients, typically a migratory arthritis involving the large joints (knees, hips, ankles, elbows), which characteristically responds dramatically to salicylate therapy. Carditis occurs in approximately 50% of cases and includes myocarditis, pericardial effusions, arrhythmias, and valvular heart disease. Erythema marginatum ( Figure 4-1 ) occurs in less than 10% of patients and is a nonpruritic serpiginous rash that occurs on the torso and is almost never seen on the face. The rash is evanescent and becomes more apparent following hot baths or being wrapped in warm blankets. Subcutaneous nodules are nontender, freely mobile nodules occurring usually over the bony surfaces of the elbows, wrists, shins, knees, ankles, and spine. They occur in 2-10% of cases. Chorea occurs in up to 15% of cases and is a neuropsychiatric disorder that may include choreiform movements, hypotonia, emotional lability, anxiety, and an obsessive-compulsive disorder. Chorea usually occurs late, after the initial pharyngitis with the average time to onset of about 6-7 months. It may last as long as 18 months. Recent evidence suggests that chorea is associated with the presence of antineuronal antibodies. Minor manifestations include fever, arthralgias (when polyarthritis is not present), increased acute phase reactants such as CRP, and a prolonged PR interval on ECG (in the absence of other evidence of carditis). The diagnosis of acute rheumatic fever is made with either 2 major manifestations or with a single major manifestation and 2 minor manifestations. If made by 1 major manifestation and 2 minors, the diagnosis should be supported by evidence of a preceding streptococcal infection either by a positive throat culture or by rising streptococcal antibody titers (eg, antistreptolysin O). There are 3 exceptions to the Jones criteria for diagnosis of acute rheumatic fever:
    1. Chorea may be the only manifestation of rheumatic fever.
    2. Indolent carditis may be the only manifestation in patients following the initial infection.
    3. Recurrences often do not strictly fulfill the Jones criteria. Therefore, a presumptive diagnosis of recurrent rheumatic fever may be made with