Non-secretory Multiple Myeloma: A Report of a Rare Case.

Multiple myeloma (MM) is a rare blood cancer. Non-measurable MM (NMMM) is a category designation consisting of both non-secretory MM (NSMM) and oligo-secretory MM (OSMM), both of which have negative findings on serum protein electrophoresis and urine protein electrophoresis testing. NSMM and OSMM are infrequent subtypes. This report describes the case of a 67-year-old female patient without significant past medical history who presented with back pain, nausea, fatigue, and mild confusion. Labs were significant for severe hypercalcemia. Imaging demonstrated osteopenia and multiple lytic lesions throughout her spine. Serum protein electrophoresis and immunofixation by electrophoresis were obtained but were inconclusive. Bone marrow biopsy was therefore obtained to help clarify the diagnosis. Workup ultimately revealed a new diagnosis of kappa light chain-restricted NSMM. It is beneficial for the clinician to review the classic features of general MM in such a case, and they are also worth reviewing, as it may be better characterized as OSMM. Recognizing the rare features of NSMM and OSMM is relevant since these are entities not commonly encountered and can appear as classic MM in the initial workup. The care of patients will continue to improve as the medical community continues to recognize the rare malignancy of MM and its variant forms of NMMM, specifically NSMM and OSMM.