Extensive myocardial disarray in hearts with normal cardiac mass: a concealed cardiomyopathic phenotype with histological overlap with hypertrophic cardiomyopathy.

Extensive myocardial disarray is a characteristic histopathological feature of hypertrophic cardiomyopathy (HCM), but its occurrence in hearts with normal cardiac mass remains poorly characterized. We reviewed 2,823 consecutive forensic autopsies and identified 1,387 hearts with normal cardiac weight. Ten cases (0.72%) demonstrated extensive type Ia myocardial disarray involving contiguous myocardial regions. Histopathological findings, clinical information, and genetic data were analyzed, and matched controls (n = 20) were selected for comparison. Disarray was accompanied by moderate-to-severe fibrosis and small intramural arterial abnormalities. Three individuals fulfilled criteria for sudden cardiac death, and none had been diagnosed with HCM during life. Matched controls lacked comparable disarray and demonstrated significantly less fibrosis. Genetic analysis identified rare variants in cardiomyopathy-associated genes, although most were classified as variants of uncertain significance. Extensive myocardial disarray and fibrosis can occur in hearts with normal cardiac mass. Although these findings do not establish a diagnosis of HCM, they define a concealed cardiomyopathic phenotype with histological overlap with HCM. Recognition of such abnormalities may improve pathological evaluation of sudden death cases currently classified as structurally normal at autopsy.