In 1963, Rheingold and colleagues introduced the terminology “smoldering acute leukemia.”³  In their case series, they described 3 patients who present with an atypical variant of acute leukemia, a clinical picture of low-grade intensity as it smolders along, symptoms of fatigue or spontaneous bruising for months to years, and unremarkable physical examination except for pallor and ecchymoses. The authors stated that “…smoldering acute leukemia is a variant of acute leukemia characterized by a prolonged and often more benign course.” In 1980, inspired by the above ideas of Rheingold and colleagues,³  Kyle and Greipp⁴  reviewed all patients diagnosed with multiple myeloma at Mayo Clinic before 1974 (N = 334), permitting at least 5 years of follow-up when writing their paper. They identified 6 cases that fulfilled criteria for the bone marrow and blood-based diagnosis of multiple myeloma (≥10% plasma cells in the bone marrow and/or ≥3 g/dL monoclonal protein in serum) but did not develop anemia, lytic bone lesions, hypercalcemia, renal failure, or other manifestations of multiple myeloma during an observation period of 5 or more years. These 6 patients were proposed to have “smoldering multiple myeloma.”⁴  Adapted from Kyle and Greipp.⁴