Review Question - QID 216612

A 57-year-old man presents to the emergency department with several days of malaise, weakness, and night sweats. Today, he experienced a headache with blurry vision, thus prompting his presentation. The patient has a history of diabetes and is followed closely by an endocrinologist. Otherwise, he has lost 10 pounds over the past month. His temperature is 100°F (37.8°C), blood pressure is 122/90 mmHg, pulse is 84/min, respirations are 16/min, and oxygen saturation is 99% on room air. Physical exam is notable for a thin man but is otherwise unremarkable. His visual acuity is 20/100 in both eyes, though he says that he normally has 20/20 vision. His gait is mildly ataxic as well, but his neurological exam is otherwise nonfocal. Laboratory studies are ordered as seen below.

Hemoglobin: 10 g/dL
Hematocrit: 31%
Leukocyte count: 57,500/mm^3 with 35% blasts
Platelet count: 109,000/mm^3

Serum:
Na+: 139 mEq/L
Cl-: 100 mEq/L
K+: 4.1 Eq/L
HCO3-: 22 mEq/L
BUN: 20 mg/dL
Glucose: 99 mg/dL
Creatinine: 1.1 mg/dL
Calcium: 10.0 mEq/L

Which of the following is the most likely diagnosis?