A 67-year-old man presents with bone pain, fatigue, and recurrent pneumonias.
Labs show calcium 12.2 mg/dL, creatinine 2.3 mg/dL, Hgb 9.1 g/dL, and total protein 10.2 g/dL.
Serum protein electrophoresis reveals an M-spike.
What is the most likely diagnosis?
