Hematology · Myeloproliferative Neoplasms
The facts most likely to be tested
Polycythemia vera is a myeloproliferative neoplasm characterized by a JAK2 mutation that leads to constitutive activation of the signaling pathway.
Patients frequently present with aquagenic pruritus, which is intense itching triggered by a warm bath or shower.
Physical examination often reveals plethora (ruddy complexion) and splenomegaly due to extramedullary hematopoiesis.
Laboratory findings demonstrate an elevated hematocrit and hemoglobin with a low serum erythropoietin (EPO) level.
The most common cause of morbidity and mortality is thrombosis, including Budd-Chiari syndrome (hepatic vein thrombosis).
First-line treatment for all patients is phlebotomy to maintain a hematocrit level of less than 45%.
High-risk patients, defined as those over age 60 or with a history of thrombosis, require the addition of hydroxyurea to reduce the risk of thrombotic events.
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A 62-year-old male presents to the clinic complaining of persistent headaches and dizziness. He reports that he experiences severe, stinging skin irritation every time he takes a hot shower. On physical exam, he has a ruddy complexion and a palpable splenomegaly. Laboratory studies reveal a hemoglobin of 19.5 g/dL, a hematocrit of 58%, and a markedly low serum erythropoietin level.
What is the most appropriate initial management for this patient?
Phlebotomy
The patient's presentation of aquagenic pruritus, plethora, and low EPO is classic for Polycythemia Vera; phlebotomy is the first-line treatment to reduce hyperviscosity and thrombotic risk.
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Etiology / Epidemiology
Myeloproliferative neoplasm driven by JAK2 mutation in patients typically >60 years old.
Clinical Manifestations
Hyperviscosity symptoms and aquagenic pruritus; plethora and splenomegaly are classic.
Diagnosis
Bone marrow biopsy is gold standard; JAK2 mutation presence with low erythropoietin levels.
Treatment
Phlebotomy is first-line; low-dose aspirin for thrombosis prevention; hydroxyurea for high-risk.
Prognosis
Risk of thrombosis is primary mortality cause; potential progression to myelofibrosis or AML.
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Epidemiology & Etiology
Polycythemia vera is a clonal stem cell disorder most common in older adults. It is characterized by the JAK2 V617F mutation in over 95% of cases. It is a primary polycythemia, distinct from secondary causes like chronic hypoxia.
Pertinent Anatomy
The disease involves the bone marrow, leading to panmyelosis. The resulting splenomegaly occurs due to extramedullary hematopoiesis as the marrow becomes hypercellular.
Pathophysiology
The JAK2 mutation leads to constitutive activation of the signaling pathway, causing cytokine-independent production of red blood cells. This results in increased blood viscosity and hypervolemia. The body responds by suppressing endogenous erythropoietin production.
Clinical Manifestations
Patients often present with aquagenic pruritus after warm showers. Physical exam reveals plethora (ruddy complexion) and splenomegaly. Thrombosis (DVT, PE, stroke) is a major red flag. Patients may also report headache, dizziness, and tinnitus due to hyperviscosity.
Diagnosis
Diagnosis requires meeting criteria including JAK2 mutation positivity and low serum erythropoietin levels. Bone marrow biopsy shows hypercellularity with prominent erythroid, granulocytic, and megakaryocytic lines. Hemoglobin thresholds are >16.5 g/dL in men or >16.0 g/dL in women.
Treatment
Initial management is phlebotomy to maintain hematocrit <45%. Low-dose aspirin is indicated for all patients to reduce thrombotic risk. Hydroxyurea is the first-line cytoreductive therapy for high-risk patients (age >60 or history of thrombosis). Avoid iron supplementation as it exacerbates erythropoiesis.
Prognosis
The primary cause of death is thrombosis or hemorrhage. Long-term monitoring is required for transformation into myelofibrosis or acute myeloid leukemia (AML). Survival is generally favorable with appropriate management.
Differential Diagnosis
Secondary Polycythemia: elevated erythropoietin levels
Essential Thrombocythemia: platelet count >450,000 without erythrocytosis
Chronic Myeloid Leukemia: presence of Philadelphia chromosome
Relative Polycythemia: normal red cell mass with decreased plasma volume
Hemoglobinopathy: high-affinity hemoglobin variants