A Case Report of a Special Type of Multiple Myeloma: <i>Kappa</i> Light Chain‐Only

ABSTRACT Multiple myeloma is a malignant tumor of the hematological system. Early diagnosis is difficult, often resulting in detection at an advanced stage, with a poor prognosis. We report a female patient diagnosed with kappa light chain multiple myeloma who initially exhibited generalized muscle aches and bone pain. Comprehensive evaluations, including serum protein electrophoresis, immunofixation electrophoresis, positron emission tomography/computed tomography, bone marrow cell morphology, immunophenotyping of lymphomas, karyotyping of bone marrow chromosomes, gene detection related to multiple myeloma using next‐generation sequencing, fluorescence in situ hybridization, pathological evaluation of renal and bone marrow biopsies, and other relevant examinations, confirmed the diagnosis of kappa light chain multiple myeloma. Unfortunately, the diagnosis was made late in the disease course, leading to a poor prognosis, and the patient's family requested treatment discontinuation. Early screening of monoclonal protein is crucial to improve patient outcomes.