question: Q:A 65-year-old man comes to the physician because of a 6-month history of muscle weakness. During this period, the patient has had low energy, intermittent nosebleeds, and a 5-kg (11-lb) weight loss. He also reports progressive hearing and vision problems. He has a history of pins-and-needles sensation, numbness, and pain in his feet. Vital signs are within normal limits. Physical examination shows a palpable liver tip 2–3 cm below the right costal margin. There is nontender lympadenopathy in the groins, axillae, and neck. Laboratory studies show:
  Hemoglobin 8.8 g/dL
  White blood cells 6,300/mm3
  Platelet count 98,000/mm3
  Erythrocyte sedimentation rate 70 mm/h
  Serum
  Na+ 136 mmol/L
  K+ 3.6 mmol/L
  Cr 1.3 mg/dL
  Ca2+ 8.6 mg/dL
  Aspartate aminotransferase 32 U/L
  Alanine aminotransferase 36 U/L
  Alkaline phosphatase 100 U/L
  Lactate dehydrogenase 120 U/L
  A serum protein electrophoresis exhibits a sharp, narrow spike of monoclonal IgM immunoglobulin. Which of the following is the most likely diagnosis?"? 
  {'A': 'Hairy cell leukemia', 'B': 'Multiple myeloma', 'C': 'Waldenstrom macroglobulinemia', 'D': 'Monoclonal gammopathy of undetermined significance', 'E': 'Mantle cell lymphoma\n"'},