A 67-year-old female patient was admitted to our hospital with skin eruptions on her legs. The skin biopsy verified a diagnosis of erythema nodosum histopathologically. The bronchoscophic biopsy was reported as chronic non-necrotizing granulomatous inflammation. FDG PET/CT revealed hypermetabolic multiple lymphadenopathy, pulmonary nodules and giant splenomegaly. The patient was treated with oral corticosteroid for the risk of splenic rupture. A complete regression was observed in the spleen and multiple lymphadenopathy. FDG PET-CT imaging may be useful to establish the treatment decision and response to treatment of extrapulmonary sarcoidosis.