A 77-year-old man presents with left-sided chest pain, headaches, night sweats, a burning sensation in his hands and feet, and shortness of breath. He began having headaches 2 days ago, and his symptoms have progressively worsened. On exam, the patient is a thin ill-appearing man. His spleen is palpated 8 cm below the costal margin, and the liver 5 cm below the costal margin. Laboratory analysis shows that his red blood cell count is elevated, and he has a decrease in plasma volume. White blood cells and platelets are within normal limits. Appearance of the red blood cells is normal. Arterial blood gas analysis shows an O2 saturation of 94% on room air. What is the most likely cause of this patient's symptoms? a. Chronic myelogenous leukemia
b. Polycythemia vera
c. Thrombocytopenia
d. Iron-deficiency anemia