Case report of isolated cardiac sarcoidosis presenting as hypertrophic obstructive cardiomyopathy-a clinical picture printed on lenticular paper.

Background: Cardiac sarcoidosis (CS) is an inflammatory granulomatous process of the myocardium that can be asymptomatic or have several different clinical phenotypes. One of its rarely described presentations consists of hypertrophy of the septal myocardium, similar to hypertrophic cardiomyopathy (HCM). Isolated cardiac sarcoidosis that haemodynamically mimics hypertrophic obstructive cardiomyopathy (HOCM) has been rarely described in the literature.

Case Summary: A 64-year-old Caucasian female previously diagnosed with non-critical aortic stenosis presented with pre-syncope, and echocardiography showed significant obstruction based on left ventricular outflow tract gradients, confirmed by cardiac magnetic resonance (CMR), concerning for a phenocopy of HCM. Septal myectomy was performed and pathology specimen revealed non-caseating granulomata consistent with cardiac sarcoidosis. She was started on oral corticosteroids and initial cardiac fluorodeoxyglucose positron emission tomography (FDG-PET) done after 1 month of treatment was negative. Repeat FDG-PET 15 months later, in the setting of haemodynamic decompensation, demonstrated diffuse FDG uptake in the myocardium without extra-cardiac involvement.

Discussion: Our case brings together two entities: isolated cardiac sarcoidosis and its presentation mimicking HOCM, which has been very rarely described in the literature. And it also shows the scenario of surgical pathology diagnosis of sarcoidosis that was not suspected by initial CMR or FDG-PET, despite adequate preparation, only appearing on repeat FDG-PET done 15 months later. Isolated cardiac sarcoidosis should remain a differential diagnosis for any non-ischaemic cardiomyopathy without a clear cause, despite imaging evidence of HCM.