A Case of Amyloid Cardiomyopathy Proved by Myocardial Biopsy but Diagnosed as Isolated Cardiac Sarcoidosis with Clinical Manifestations

A 74-year-old man with dyspnea on exertion was referred to our hospital for treatment of heart failure and evaluation of the cause. The symptom was immediately improved by medical therapy including oxygenation and diuretics. Electrocardiography showed frequent premature ventricular contraction with non-sustained ventricular tachycardia. Echocardiography revealed left ventricular (LV) dilatation (LV end-diastolic diameter/end-systolic diameter = 64/56 mm), thinning of the basal interventricular septum with severe hypokinesis of the region and LV systolic dysfunction (LVEF = 25%). Coronary angiography showed patent coronary artery. Late gadolinium enhancement in cardiac MR imaging was observed in septal to anterior wall. Furthermore, his lysozyme value was high (13.6 µg/mL). Cardiac sarcoidosis was strongly suspected, and 18F-fluorodeoxy glucose-positron emission tomography imaging showed lightly increased uptake in interventricular septum. Although he did not have the clinical findings other than heart, based on current guidelines for diagnosis and treatment of cardiac sarcoidosis (JCS 2016), a diagnosis of isolated cardiac sarcoidosis was finally made and we decided to start corticosteroid therapy with the initial dose of 30 mg/day of prednisolone. However, the specimens of myocardial biopsy revealed significant amount of transthyretin amyloid deposit. In addition 99mTc-pyrophosphate scintigraphy showed increased uptake by interventricular septum. In this case, there are two possibilities: first, all clinical manifestations due to transthyretin cardiac amyloidosis, and second, a chance complication with cardiac sarcoidosis and amyloid cardiomyopathy.