Rationale: We report a case of successful diagnosis of POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes) syndrome based on monoclonality that was confirmed by an osteosclerotic lesion biopsy in a patient without pathognomonic symptoms or monoclonal gammopathy, probably because of comorbidities, which included systemic lupus erythematosus, rheumatoid arthritis, and Sjögren syndrome.
Patient concerns: A 57-year-old woman presented with an approximately 2-year history of numbness in the toes that had gradually spread, along with muscle weakness in both arms and legs. She had been receiving immunosuppressant and corticosteroid therapy since being diagnosed with systemic lupus erythematosus and Sjögren syndrome at the age of 31 years and rheumatoid arthritis at the age of 44 years. Neurological examination revealed predominantly distal hypoesthesia and weakness in a typical stocking-and-glove pattern. Immunoelectrophoresis revealed elevated polyclonal immunoglobulin, which was attributed to her known underlying disease.
Diagnoses: Biopsy of an osteosclerotic lesion confirmed proliferation of monoclonal plasma cells, leading to a diagnosis of POEMS syndrome.
Interventions and outcomes: Lenalidomide therapy was started after the diagnosis and the patient had a favorable outcome.
Lessons: Osteosclerotic lesion biopsy can be useful for diagnosis of POEMS syndrome in difficult cases.