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Difficulty: EasyHematology and Oncology

A 6161-year-old man comes to the clinic for evaluation of frequent headaches, dizziness, and generalized pruritus that severely worsens after he takes a warm shower. He has a history of mild chronic obstructive pulmonary disease (COPD) and a 3535-pack-year smoking history. Vital signs show a blood pressure of 148/92 mm Hg148/92\text{ mm Hg}, pulse of 82/min82/\text{min}, and respiratory rate of 14/min14/\text{min}. Pulse oximetry is 96%96\% on room air. Physical examination reveals a ruddy facial complexion and a palpable spleen tip 3 cm3\text{ cm} below the left costal margin. Laboratory studies reveal the following:

MeasurementResultReference Range
Hemoglobin19.5 g/dL19.5\text{ g/dL}13.5−17.5 g/dL13.5-17.5\text{ g/dL}
Hematocrit61%61\%41%−53%41\%-53\%
Leukocytes14,800/mm314,800/\text{mm}^34,500−11,000/mm34,500-11,000/\text{mm}^3
Platelets550,000/mm3550,000/\text{mm}^3150,000−400,000/mm3150,000-400,000/\text{mm}^3
Serum erythropoietinLowNormal

Which of the following is the most appropriate next step in management?

  1. Initiate therapeutic phlebotomyAnswer
  2. B
    Obtain an arterial blood gas to calculate acid-base compensation
  3. C
    Administer systemic corticosteroids and nebulized bronchodilators
  4. D
    Prescribe empiric broad-spectrum antibiotics
  5. E
    Measure serum thyroid-stimulating hormone levels

Answer

Initiate therapeutic phlebotomy
The correct answer is to initiate therapeutic phlebotomy. This patient's presentation of aquagenic pruritus (severe itching after a warm shower), facial plethora, headaches, and splenomegaly is highly classic for Polycythemia Vera (PV). The laboratory findings of panmyelosis (elevated hemoglobin, leukocytes, and platelets) combined with a low serum erythropoietin (EPO) level secure the diagnosis of primary polycythemia over secondary causes. PV is driven by an activating mutation in the JAK2 kinase, leading to EPO-independent proliferation of myeloid cell lines. The primary morbidity and mortality in PV arise from hyperviscosity-induced thrombosis. Therefore, the immediate next step in management is therapeutic phlebotomy to lower the hematocrit to less than 45%45\%, which significantly reduces the risk of thrombotic complications.

Step-by-Step Solution

1
Analyze the patient's classic symptoms and physical exam findings.
The patient has aquagenic pruritus (itching after a warm shower), headaches, dizziness, a ruddy complexion (plethora), and splenomegaly.
These are hallmark clinical features of hyperviscosity and histamine release associated with myeloproliferative neoplasms.
2
Evaluate the complete blood count and serum erythropoietin levels.
The labs show panmyelosis (elevated red blood cells, white blood cells, and platelets) alongside a low serum erythropoietin (EPO) level.
A low EPO level distinguishes primary polycythemia (Polycythemia Vera) from secondary polycythemia, where EPO would be elevated due to chronic hypoxia or an EPO-secreting tumor.
3
Determine the most appropriate initial management for the diagnosed condition.
The patient requires immediate reduction of red cell mass via therapeutic phlebotomy.
Lowering the hematocrit to below 45% is critical in Polycythemia Vera to mitigate the high risk of fatal thrombotic events (e.g., stroke, myocardial infarction).

Key Concept

Polycythemia Vera is a primary myeloproliferative neoplasm characterized by panmyelosis, a low serum erythropoietin level, and classic symptoms like aquagenic pruritus. Initial management is therapeutic phlebotomy to lower the hematocrit and reduce thrombotic risk.
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Topics

Hematology and Oncology

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