Systemic reactive angioendotheliomatosis mimicking hypertrophic cardiomyopathy in a domestic shorthair cat

A two-year-old, 3.9-kg, male castrated, domestic shorthair cat presented to The Ohio State University Veterinary Medical Center for acute onset neurological signs. During hospitalization, he was diagnosed with an American College of Veterinary Internal Medicine (ACVIM) stage B1 hypertrophic cardiomyopathy phenotype on echocardiogram. His clinical signs acutely worsened, including seizure activity and panting, and he was euthanized. Necropsy revealed the histopathologic diagnosis of systemic reactive angioendotheliomatosis, which notably severely affected the myocardium. In this case report, we present the antemortem diagnostic results and postmortem necropsy results of this rare condition in cats. This case demonstrates that echocardiographic assessment of the heart in cats affected by systemic reactive angioendotheliomatosis may lead to the false diagnosis of hypertrophic cardiomyopathy and thus should be considered as a differential diagnosis in cats with symmetrical left ventricularl wall thickening on echocardiography.