A 60-year-old man comes to the office due to 6 months of exertional dyspnea and occasional headaches. He has had no chest pain, lightheadedness, or syncope. The patient injured his knee 8 months ago and required arthroscopic ligament repair. Due to restricted physical activity after surgery, he has gained 4.5-6.8 kg (10-15 lb) . He also has a history of gastroesophageal reflux disease and seasonal allergies. The patient was a heavy smoker but quit a year ago after being hospitalized with community-acquired pneumonia. He drinks 6 beers daily and occasionally more on weekends.
Blood pressure is 145/100 mm Hg, pulse is 95/min, and oxygen saturation is 93% on room air. BMI is 34 kg/m². Cardiopulmonary auscultation reveals no abnormalities. A smooth liver edge is palpated 2 cm below the right costal margin. The tip of the spleen is palpable with deep inspiration. There is no peripheral edema.
Laboratory results are as follows:
Repeat hemoglobin level is 18.5 g/dL.
Which of the following is most likely to establish the cause of polycythemia in this patient?

Question

A 60-year-old man comes to the office due to 6 months of exertional dyspnea and occasional headaches. He has had no chest pain, lightheadedness, or syncope. The patient injured his knee 8 months ago and required arthroscopic ligament repair. Due to restricted physical activity after surgery, he has gained 4.5-6.8 kg (10-15 lb) . He also has a history of gastroesophageal reflux disease and seasonal allergies. The patient was a heavy smoker but quit a year ago after being hospitalized with community-acquired pneumonia. He drinks 6 beers daily and occasionally more on weekends.
Blood pressure is 145/100 mm Hg, pulse is 95/min, and oxygen saturation is 93% on room air. BMI is 34 kg/m². Cardiopulmonary auscultation reveals no abnormalities. A smooth liver edge is palpated 2 cm below the right costal margin. The tip of the spleen is palpable with deep inspiration. There is no peripheral edema.
Laboratory results are as follows:

Repeat hemoglobin level is 18.5 g/dL.
Which of the following is most likely to establish the cause of polycythemia in this patient?

Quizplus · Accepted Answer

11ec193a_9826_582c_853d_1bd72b7e096e_MD0002_00 This patient has polycythemia, which is defined as hemoglobin >16 g/dL in women and >16.5 g/dL in men. Polycythemia can be due to myriad causes but is typically divided into: Primary polycythemia - acquired or inherited mutation of a red blood cell progenitor cell leads to erythropoietin (EPO)-independent erythrocytosis. EPO levels are typically low. Polycythemia vera is the most common cause and is typically diagnosed by JAK2 mutation testing (positive in >97%) and bone marrow biopsy (Choices B and D).Secondary polycythemia - erythrocytosis is driven by a circulating factor (usually EPO) that stimulates red blood cell production. EPO levels are typically elevated. Most cases (>90%) are due to hypoxia, which stimulates the kidneys to produce EPO. Less common causes include EPO-secreting tumors (eg, renal or hepatocellular) and testosterone supplementation. Primary polycythemia - acquired or inherited mutation of a red blood cell progenitor cell leads to erythropoietin (EPO)-independent erythrocytosis. EPO levels are typically low. Polycythemia vera is the most common cause and is typically diagnosed by JAK2 mutation testing (positive in >97%) and bone marrow biopsy (Choices B and D). Primary polycythemia - acquired or inherited mutation of a red blood cell progenitor cell leads to erythropoietin (EPO)-independent erythrocytosis. EPO levels are typically low. Polycythemia vera is the most common cause and is typically diagnosed by JAK2 mutation testing (positive in >97%) and bone marrow biopsy (Choices B and D). Secondary polycythemia - erythrocytosis is driven by a circulating factor (usually EPO) that stimulates red blood cell production. EPO levels are typically elevated. Most cases (>90%) are due to hypoxia, which stimulates the kidneys to produce EPO. Less common causes include EPO-secreting tumors (eg, renal or hepatocellular) and testosterone supplementation. Secondary polycythemia - erythrocytosis is driven by a circulating factor (usually EPO) that stimulates red blood cell production. EPO levels are typically elevated. Most cases (>90%) are due to hypoxia, which stimulates the kidneys to produce EPO. Less common causes include EPO-secreting tumors (eg, renal or hepatocellular) and testosterone supplementation. This patient's polycythemia is associated with high EPO levels, suggesting a secondary cause. Given his history of cigarette use, obesity, and dyspnea, the most likely underlying driver is pulmonary disease (eg, cigarette use, sleep apnea) leading to hypoxia. Confirmation can be made using post-exercise and nocturnal oxygen saturation testing. (Choice A) Measurement of blood volume can help distinguish relative from absolute polycythemia. Severe dehydration can lead to a relative polycythemia that is corrected with fluid repletion. (Choice C) CT scan of the abdomen with contrast can be used to evaluate for an EPO-producing tumor of the liver or kidney. However, abdominal CT scan is usually reserved for those with normal oxygen saturation testing or manifestations suggestive of malignancy (eg, abdominal/flank pain, jaundice, hematuria, abdominal mass). This patient's hepatosplenomegaly (with a smooth liver edge) and thrombocytopenia likely represent alcohol-mediated end-organ damage rather than signs of malignancy. Educational objective: Polycythemia is defined as a hemoglobin level >16 g/dL in women and >16.5 g/dL in men and is typically categorized into primary and secondary causes. Primary polycythemia is erythropoietin (EPO)-independent and is usually associated with low EPO levels; polycythemia vera is the most common cause and is usually diagnosed by JAK2 mutation testing and bone marrow biopsy. Secondary polycythemia is usually EPO-dependent and marked by high EPO levels; hypoxia is the most common cause and is typically diagnosed by oxygen saturation testing at rest, after exercise, and during sleep. __________ References: Polycythemia vera and essential thrombocythemia: 2012 update on diagnosis, risk stratification, and management. (http://www.ncbi.nlm.nih.gov/pubmed/22331582) Testosterone suppresses hepcidin in men: a potential mechanism for testosterone-induced erythrocytosis. (http://www.ncbi.nlm.nih.gov/pubmed/20660052)

A 60-Year-Old Man Comes to the Office Due to 6