What histologic changes are seen in hypertrophic cardiomyopathy?

• A. Hypertrophy of myocardial fibers with interstitial fibrosis
• B. Diffuse lymphocytic infiltration
• C. Fatty infiltration
• D. Calcification

Answer: (A)

Hypertrophic cardiomyopathy causes thickened heart muscle with enlarged myocytes arranged in disarray and accompanied by interstitial fibrosis. This combination—myocyte hypertrophy plus fibrosis (and the disorganized fiber pattern you’d expect to see on histology)—is what leads to the stiff, noncompliant ventricle and the risk of arrhythmias. Among the options, hypertrophy of myocardial fibers with interstitial fibrosis best reflects these histologic changes. Diffuse lymphocytic infiltration would point to myocarditis, fatty infiltration to conditions like fatty replacement/ARVC, and calcification is not typical of HCM.