Myeloma comprises a spectrum of conditions: monoclonal gammopathy of undetermined significance (MGUS), asymptomatic myeloma (classified as smoldering myeloma or indolent myeloma), and symptomatic (or overt) myeloma. Disease classification is an important part of diagnosing myeloma because it dictates the approach to clinically managing a patient’s disease.
MGUS: This benign precursor condition does not produce symptoms but can be detected by excess amounts of M protein. The condition is not treated, but it is monitored because it progresses to malignant disease in about 20-25% of patients.
Asymptomatic myeloma: With asymptomatic myeloma, M protein levels are slightly elevated (higher than with MGUS), and the percentage of plasma cells in the bone marrow is elevated. However, any symptoms such as anemia or bone lesions are mild, and the severe symptoms of symptomatic myeloma are not present.
Symptomatic myeloma: For this disease, immediate treatment is warranted. Symptomatic myeloma is characterized by elevated levels of M protein and plasma cells and by symptoms of anemia, renal failure, hypercalcemia, or osteolytic lesions. A small subset of patients (less than 5%) with symptomatic myeloma have nonsecretory disease, which means that their malignant plasma cells do not secrete M protein (learn more about nonsecretory myeloma in an article written by Bijay Nair, MD, MPH, former physician at the Myeloma Institute).