True non-secretory multiple myeloma in a resource-limited setting: A diagnostic challenge

True non-secretory multiple myeloma (NSMM), defined by absent monoclonal protein on serum/urine electrophoresis, immunofixation, and free light-chain assay, accounts for <1% of myeloma cases. We report a 49-year-old male with recurrent fever and bone pain in whom all serologic markers were negative; a weakly positive anti-Ro antibody initially suggested autoimmune disease. Fluorodeoxyglucose positron emission tomography computed tomography (PET-CT) revealed diffuse hypermetabolic axial marrow involvement, and bone marrow biopsy confirmed 12% clonal plasma cells cluster of differentiation ([CD]38/CD138/CD56-positive), establishing International Staging System stage II NSMM. Bortezomib-lenalidomide-dexamethasone achieved minimal residual disease (MRD)-negative stringent complete response with complete metabolic response by PET-CT and multiparametric flow cytometry after four cycles. He remains on lenalidomide maintenance at 12 months. Negative electrophoresis does not exclude myeloma; PET-CT and marrow-based MRD assessment are indispensable in NSMM.