Sarcoidosis is a multi-systemic inflammatory disorder of unknown cause characterized by the formation of non-caseating granulomas in involved organs. Its cardiac involvement may be potentially fatal. Although endomyocardial biopsy is required for definitive diagnosis of cardiac sarcoidosis, it is invasive and lacks sensitivity. The specific diagnostic tool for cardiac sarcoidosis is far from satisfactory. Recent studies have revealed that FDG-PET with under fasting conditions is a useful method for identification of cardiac sarcoidosis patients. However, to our knowledge, no investigations have been published with regard to FDG quantification for the diagnosis and management of cardiac sarcoidosis by PET.

Fasting FDG-PET will be performed in all subjects. Serum calcium, C-reactive protein (CRP), angiotensin converting enzyme (ACE), lysozyme, and B-type natriuretic peptide (BNP) levels will be measured in all patients. All patients will undergo chest X-ray, resting 12-lead ECG, transthoracic echocardiography, and 3 types of radionucleotide imaging using Tc-99m sestamibi for myocardial perfusion, Ga and FDG for whole-body evaluation. All assessments will be conducted within 2 weeks and no sign indicated any change in disease activity of sarcoidosis. The patients with cardiac involvement will be treated with 30 mg/day of prednisolone orally for the first 4 weeks, then will decrease to a dose of 20 mg/day for the next 4 weeks, and will maintain to a dose of 10 mg/day afterwards.

Inclusion Criteria:

• Subjects between the ages of 35 and 85 years
• Subjects with systemic sarcoidosis
• Subjects with idiopathic sarcoidosis

Exclusion Criteria:

• Subjects with active inflammatory diseases not related to sarcoidosis
• Subjects with coronary artery disease and primary valvular heart diseases
• Subjects with uncontrolled diabetes mellitus or insulin treatment
• Subjects with use of the corticosteroid
• Subjects with systemic disorders such as active inflammatory, liver, renal, hematopoietic, and malignant disease

Fasting FDG-PET will be performed in patients with sarcoidosis and age-matched DCM patients. Among them, systemic sarcoidosis will be diagnosed clinically and/or histologically, and referred for cardiac sarcoidosis. Patients with sarcoidosis will reveal cardiac involvement based on guidelines established in 2006 by the Japanese Ministry of Health and Welfare. Healthy control subjects will undergo FDG-PET.