Cardiac Sarcoidosis Mimicking Septal Tumor with Intermittent Complete Atrioventricular Block.

A 52-year-old woman with intermittent complete atrioventricular (AV) block detected on exercise was admitted to the hospital. Echocardiography revealed lesions on the right ventricular side of the interventricular septum and free wall of the basal inferolateral area. Gadolinium-enhanced cardiovascular magnetic resonance (CMR) imaging revealed the mass and wall thickening at the same locations with late gadolinium enhancement (LGE). Focal uptake at the septal lesion was detected using 67Ga scintigraphy. Focal on diffuse intense uptake in the lesions was observed on Fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) imaging. Whole-body CT and laboratory evaluations uncovered no signs of malignant tumors in other organs. Ophthalmologic evaluation revealed ophthalmologic sarcoidosis. Although the result of endomyocardial biopsy was negative, the presence of cardiac sarcoidosis was strongly suggested on the basis of the new Japanese guidelines published in 2017. AV conduction disturbance and tracer accumulation on 67Ga scintigraphy completely disappeared after 2 weeks of steroid therapy. The size of mass, inferolateral wall thickness in echocardiography and CMR, and standardized uptake value (SUV) of the masses on 18F-FDG PET also decreased over time.