Multiple myeloma is a cancer of plasma cells, antibody-producing cells that usually reside in bone marrow. Malignant plasma cells accumulate and commonly produce an abnormal antibody or antibody fragment. The disease can affect several parts of the skeleton and cause bone damage, kidney impairment, reduced blood-cell production, and weakened immunity. (cancer.gov)
Biological features
Normal plasma cells develop from B cells and produce antibodies that help defend against infection. In myeloma, a malignant population produces a relatively uniform immunoglobulin, called a monoclonal protein or M protein, or free immunoglobulin light chains. These proteins can accumulate in blood or urine. Meanwhile, production of normal antibodies may decline, reducing the effectiveness of the immune system. (cancer.gov)
Related plasma-cell disorders
Myeloma is distinguished from several related conditions:
- Monoclonal gammopathy of undetermined significance (MGUS): a small abnormal plasma-cell population without myeloma-defining organ damage.
- Smoldering multiple myeloma: a greater plasma-cell or monoclonal-protein burden, but no myeloma-defining event.
- Solitary plasmacytoma: a localized plasma-cell tumor without the findings required for systemic myeloma.
MGUS and smoldering myeloma can progress to active disease, but progression is not inevitable. (myeloma.org)
Clinical manifestations
Common manifestations include bone pain, fractures, fatigue associated with anemia, recurrent infections, elevated blood calcium, and kidney dysfunction. Vertebral damage may cause spinal cord compression. Some patients initially have few symptoms, and the disease is detected through abnormal laboratory results. Excess abnormal light chains can also be associated with amyloidosis, in which protein deposits damage tissues and organs. (cancer.gov)
Diagnosis
Evaluation combines blood and urine studies, bone-marrow biopsy, and imaging. Tests identify monoclonal proteins, measure free light chains, and assess blood counts, calcium, and kidney function. Computed tomography, PET combined with CT, and magnetic resonance imaging can identify skeletal or marrow abnormalities. An M protein alone does not establish myeloma. (cancer.gov)
International Myeloma Working Group criteria require an adequate clonal plasma-cell population—generally at least 10% of marrow cells—or a biopsy-confirmed plasmacytoma, together with a myeloma-defining event. Such events include attributable CRAB abnormalities: elevated calcium, renal impairment, anemia, or destructive bone lesions. Alternatively, qualifying biomarkers are:
- At least 60% clonal marrow plasma cells.
- An involved-to-uninvolved serum free-light-chain ratio of at least 100, with the involved light chain at least 100 mg/L.
- More than one MRI focal lesion, each at least 5 mm.
Consequently, active myeloma can be diagnosed before symptomatic organ damage develops. (myeloma.org)
Treatment
Treatment generally uses combinations of drugs, including proteasome inhibitors, immunomodulatory agents, corticosteroids, and monoclonal antibodies. Selected patients receive high-dose chemotherapy followed by autologous hematopoietic stem-cell transplantation, using their own collected stem cells. Maintenance therapy can prolong disease control. CAR T-cell therapy and bispecific antibodies are among treatments used for relapsed or refractory disease. (cancer.gov)
Radiation therapy may control localized painful lesions. Supportive treatment addresses skeletal complications, infection, anemia, kidney impairment, and treatment-related adverse effects. (cancer.gov)
Epidemiology and prognosis
Myeloma predominantly affects older adults. U.S. SEER data for 2019–2023 report a median diagnostic age of 69 and an age-adjusted annual incidence of 7.4 cases per 100,000 people. Incidence is higher in men than women and in non-Hispanic Black populations than in other reported racial and ethnic groups. (seer.cancer.gov)
The clinical course varies with disease biology, organ function, and treatment response. Myeloma is generally not considered curable with standard treatment, although prolonged remissions occur. Relapse remains a major feature of its course. (cancer.gov)
For U.S. diagnoses during 2016–2022, SEER reports five-year relative survival of 63.7%. Relative survival compares survival among patients with that expected in a comparable general population; it is a population measure, not a prediction for an individual. (seer.cancer.gov)