POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes) syndrome is rare, with polyneuropathy and monoclonal plasma cell disorder generally considered as essential diagnostic symptoms. We report two cases of POEMS syndrome without monoclonal protein expression. The first case was a 72-year-old man who had experienced recurrent edema of the lower limbs for 2 years and abdominal distention for 2 months. The other case was a 62-year-old man with a 5-year history of recurrent numbness of the extremities and muscle weakness, which had become serious over the preceding 3 months. Both patients had various symptoms that matched those of POEMS syndrome, but neither had monoclonal protein expression. However, a diagnosis of POEMS syndrome was made in each case. Both patients were treated with lenalidomide and dexamethasone, after which their symptoms improved and laboratory test results normalized. The findings in these two cases suggest the possibility that POEMS syndrome may occur without monoclonal protein expression. The diagnostic criteria of POEMS syndrome may thus need further investigation.
Keywords: POEMS syndrome; atypical; case report; diagnostic criteria; monoclonal protein; symptom.