- Diagnosis of smoldering multiple myeloma or monoclonal gammopathy of undetermined significance (MGUS). Smoldering multiple myeloma is defined as asymptomatic multiple myeloma with absence of lytic bone lesions. MGUS is defined by presence of serum monoclonal protein <3 g/dL; absence of lytic bone lesions, anemia, hypercalcemia, and renal insufficiency related to the monoclonal protein; and (if determined) proportion of plasma cells in the bone marrow of 10% or less.