Polycythemia vera PV

Definition

• T In RBC mass • i granulocytes and platelets in the absence of physiologic stimulus Etiologies of erythrocytosis

• Relative t RBC (. plasma): dehydration; "stress" erythrocytosis (Gaisbock's syndrome)

• Absolute t RBC: 1° (PV. other MPD) or 2° due to hypoxia; carboxyhemoglobinemia;

inappropriate erythropoietin (renal, hepatic, cerebellar tumors): Cushing's syndrome

Clinical manifestations (common between PV and ET)

• Symptoms — often termed "vasomotor symptoms"

hyperviscosity (erythrocytosis): headache, dizziness, tinnitus, blurred vision ^^^ thrombosis (hyperviscosity, thrombocytosis): transient visual disturbances (amaurosis.

ocular migraine); Budd-Chiari syndrome: erythromelalgia intense burning, pain, and erythema of extremities due to microvascular thrombi bleeding (abnormal platelet function): easy bruising, epistaxis. Gl bleeding T histamine from basophils • pruritus, peptic ulcers; t uric acid (cell turnover) — gout

• Signs: plethora, splenomegaly, hypertension, engorged retinal veins

Diagnostic evaluation

• /Epo to rule out secondary causes of erythrocytosis; If epo 1. PV likely

If epo T. then ✓ SaOj or PaOj. carboxyhemoglobin

• Red cell mass is diagnostic "gold standard" test but not commonly done

• i ' WBC. platelets, basophils; * uric acid, leukocyte alkaline phosphatase, vitamin Bu

• Peripheral smear — no morphologic abnormalities

• BM bx — hypercellular. megakaryocyte hyperplasia, i iron, absence of Ph chromosome Treatment

• Phlebotomy to moderate degree of Fe deficiency -» Hct <45% (men) or 42% (women)

• Hydroxyurea if high risk of thrombosis (age -60. prior thrombosis) or symptomatic thrombocytosis (pit >1.5 X 106 ixl)

• Supportive: allopurinol (gout). Hj-blockers antihistamines (pruritus)

Prognosis

• Median survival 9-12 y with transformation into acute leukemia in 2% of cases

• Post-PV myeloid metaplasia (spent phase) occurs in 15% of cases, usually after 10 y

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