A 38-year-old obese man presents with fatigue. The patient reports several bouts of daytime sleepiness in the past 6 months. He is accompanied by his wife who reports that he snores excessively each night, and that this is causing a strain on their relationship. On physical examination, the patient has a blood pressure of 158/92 mmHg and a BMI of 34 kg/m2 . The rest of the physical examination is unremarkable. Laboratory studies reveal the following:
Which of the following explains this patient’s laboratory abnormalities?
A. Hypoxemia-induced increase in erythropoietinHypoxemia-induced increase in erythropoietin. The patient in this question is presenting with signs and symptoms consistent with a diagnosis of obstructive sleep apnea (OSA). OSA is a disease with recurrent transient obstruction of the upper airway due to pharyngeal collapse. Patients tend to be overweight and complain of daytime sleepiness, snoring, headaches, and other symptoms suggesting hypertension. Importantly, OSA episodes create a state of hypoxemia that subsequently causes the kidneys to increase erythropoietin production. Erythropoietin in turn stimulates the creation of more RBCs causing polycythemia.
(B) This answer is consistent with a diagnosis of polycythemia vera, which is a primary cause of polycythemia (as opposed to hypoxemia, which is a secondary cause) that may also present with an increase in all blood cell lines. (C) This answer is consistent with a diagnosis of CML, which would cause leukocytosis (not seen with this patient). (D) Cobalamin (vitamin B12) deficiency causes megaloblastic anemia with hypersegmented neutrophils on peripheral blood smear.