POEMS syndrome misdiagnosed as bone metastasis in a patient with thyroid cancer

Polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes (POEMS) syndrome is a monoclonal plasma cell disorder. Patients with POEMS syndrome also have various clinical manifestations including generalized edema, pleural effusion, ascites, papilledema, and sclerotic bone lesions. These manifestations can lead to a misdiagnosis or delayed diagnosis. We recently experienced a 51-year-old male patient with POEMS syndrome whose sclerotic bone lesion was misdiagnosed as malignant bone metastasis of papillary thyroid carcinoma. We reassessed the patient and found polyneuropathy, hepatosplenomegaly, hypothyroidism, partial hypopituitarism, immunoglobulin G lambda-type monoclonal gammopathy, hypertrichosis, ascites, and multiple sclerotic bone lesions, all of which led us to a diagnosis of POEMS syndrome. Treatment with thalidomide and dexamethasone resulted in clinical and radiological improvement. The patient has remained in remission after peripheral blood stem cell transplantation.