Review Question - QID 109938

A 59-year-old man presents to his primary care physician for fatigue. In general, he has been in good health; however, he recently has experienced weight loss, abdominal pain, and general fatigue. He has a medical history of anxiety, diabetes, a fracture of his foot sustained when he tripped, and a recent cold that caused him to miss work for 1 week. His current medications include metformin, insulin, buspirone, vitamin D, calcium, and sodium docusate. His temperature is 99.5°F (37.5°C), blood pressure is 150/100 mmHg, pulse is 90/min, respirations are 18/min, and oxygen saturation is 98% on room air. Physical exam reveals a calm gentleman. A mild systolic murmur is heard in the left upper sternal region. The rest of the physical exam is within normal limits. Laboratory values are ordered as seen below.

Hemoglobin: 12 g/dL
Hematocrit: 36%
Leukocyte count: 66,500/mm^3 with normal differential
Platelet count: 177,000/mm^3
Leukocyte alkaline phosphatase: elevated

Serum:
Na+: 139 mEq/L
Cl-: 100 mEq/L
K+: 4.3 mEq/L
BUN: 20 mg/dL
Glucose: 120 mg/dL
Creatinine: 1.1 mg/dL
Ca2+: 10.9 mEq/L
AST: 12 U/L
ALT: 10 U/L

Which of the following is the most likely diagnosis?