Hypertrophic cardiomyopathy (HCM) is pathologically characterized by which histological finding on endomyocardial biopsy?
- A Interstitial fibrosis with inflammatory infiltrate and myocyte necrosis
- B Diffuse amyloid deposition between myofibers causing a 'stiff' cardiomyopathy
- C Myofiber disarray (haphazard arrangement of hypertrophied cardiomyocytes), interstitial fibrosis, and abnormal intramural coronary arteries ✓
- D Dilated chambers with thin walls and uniformly hypertrophied myocytes
Correct answer: C. Myofiber disarray (haphazard arrangement of hypertrophied cardiomyocytes), interstitial fibrosis, and abnormal intramural coronary arteries
Explanation
HCM is characterized histologically by myofiber disarray — cardiomyocytes are arranged in chaotic, swirling patterns rather than parallel alignment — along with myocyte hypertrophy, interstitial fibrosis, and dysplastic small intramural coronary arteries. This pattern is absent in other cardiomyopathies. HCM is caused by mutations in sarcomeric proteins (most commonly beta-myosin heavy chain, myosin-binding protein C).
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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