A 10-year-old boy is brought to the emergency department due to shortness of breath and palpitations for the past day. He also has associated fever and fatigue. Vital signs indicate tachypnea, tachycardia, and hypotension. On cardiac auscultation, the patient has a new holosystolic murmur. He is admitted to the hospital for further workup and management. A cardiac biopsy is performed due to decompensation and an unclear diagnosis. Light microscopy of the tissue specimen is shown in the image below.
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Which of the following most likely preceded development of this patient's current condition?
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Acute rheumatic fever (ARF) is an immune-mediated complication of an untreated group A streptococcal pharyngeal infection. The most serious manifestation of ARF is pancarditis, which can cause nonspecific fever, fatigue, and anorexia as well as altered vital signs (tachycardia, tachypnea, hypotension). Endocardial involvement resulting in valvular dysfunction (specifically acute mitral valve regurgitation) is the most likely cause of the patient's new holosystolic murmur.
This patient's myocardial biopsy shows a lesion consisting of lymphocytes and macrophages as well as scattered multinucleated giant cells. This interstitial myocardial granuloma, or Aschoff body, is pathognomonic for ARF-related myocarditis. Plump macrophages with abundant cytoplasm and central, slender chromatin ribbons called Anitschkow (or caterpillar) cells are also often present. Over subsequent years, Aschoff bodies are replaced by fibrous scar tissue, leading to chronic mitral valve stenosis and regurgitation.
(Choice A) Hypersensitivity myocarditis, which results from an autoimmune reaction to a medication, is characterized by an interstitial infiltrate of eosinophils. Many classes of drugs, including diuretics (eg, furosemide, hydrochlorothiazide) and antibiotics (eg, ampicillin, azithromycin), can cause this hypersensitivity reaction.
(Choice C) Anthracyclines (eg, doxorubicin, daunorubicin) are cardiotoxic chemotherapeutic agents. These agents can cause dose-related acute and chronic cardiac damage (eg, dilated cardiomyopathy). On biopsy, patchy fibrosis with vacuolization and lysis of myocytes are evident.
(Choice D) A genetic mutation involving sarcomere genes can lead to the development of hypertrophic cardiomyopathy (HCM). HCM leads to left ventricular hypertrophy and, in turn, both systolic and diastolic dysfunction. The pathology involves disorganized, hypertrophied myocytes.
(Choice E) Recent travel to South America is associated with Chagas disease, which is caused by the protozoan parasite Trypanosoma cruzi. Chagas disease can result in a myocarditis characterized by distension of individual myofibers with intracellular trypanosomes.
(Choice F) Viral myocarditis produces a predominantly lymphocytic interstitial infiltrate with focal necrosis of myocytes. Aschoff bodies are not seen. Viral infection (eg, adenovirus, Coxsackie B virus, parvovirus B19) is the most common cause of myocarditis in the general population.
Educational objective:
Interstitial myocardial granulomas (Aschoff bodies) are found in carditis due to acute rheumatic fever, which develops after an untreated group A streptococcal pharyngeal infection. Aschoff bodies contain plump macrophages with abundant cytoplasm and central, slender ribbons of chromatin (Anitschkow, or caterpillar, cells).