5.15.09 Gibbs. PCV

Congratulations Hurricanes! : 

Congratulations Hurricanes! 3-2 win over #1 seed Boston Bruins to win series

Polycythemia Vera : 

Polycythemia Vera Wood Gibbs AM Report 2/27/2008

Introduction : 

Introduction One of the chronic myeloproliferative disorders Polycythemia Vera (PCV) Essential Thrombocytopenia (ET) Chronic myelogenous leukemia (CML) Myelofibrosis with myeloid metaplasia Characterized by increased red blood cell mass or erythrocytosis

Incidence : 

Incidence Median age of diagnosis is 60 but seen in wide age range between 20 and 85 Slightly higher incidence in men than women (2.8 vs. 1.3 cases/100,000 per year, respectively) Survival of untreated PCV estimated between 6 to 18 months but treated patient survival is >10years

Causes of Death in PCV : 

Causes of Death in PCV Thrombosis (29%) Hematologic malignancies (ie AML or MDS, 23%) Rate of hematologic transformation ~1.3 episodes per 100 patient years Non-hematologic malignancies (16%) Hemorrhage (7%) Myeloid metaplasia with myelofibrosis (3%)

Clinical Presentation : 

Clinical Presentation Pruritus Especially following vigorous rubbing of skin after warm bath or shower Suggested that mast cell degranulation and release of histamine play a role Also release of adenosine diphosphate from red cells or catecholamines from adrenergic vasoconstrictor nerves when skin is cooled may cause plt aggregation and local production of pruritogenic factors

Clinical Presentation : 

Clinical Presentation Erythromelalgia Burning pain in feet or hands accompanied by erythema, pallor, or cyanosis in presence of palpable pulses Microvascular thrombotic complication in PCV and ET

Clinical Presentation : 

Clinical Presentation Thrombosis Secondary to increases in blood viscosity and platelet number 15% of PCV pts with a prior major thrombotic complication (ie CVA, MI, thrombophlebitis, DVT, PE) De novo presentation of thrombosis in pts with Budd-Chiari syndrome and portal, splenic, or mesenteric vein thrombosis Suspect PCV in pts with these diagnosis under age of 45.

Clinical Presentation : 

Clinical Presentation GI sxs High incidence of epigastric distress, h/o PUD, and gastroduodenal erosions on upper endoscopy Felt 2/2 alterations in gastric mucosal blood flow due to altered blood viscosity and/or increased histamine release from tissue basophils

Physical Exam : 

Physical Exam Splenomegaly Facial plethora (ruddy cyanosis) Hepatomegaly Injection of conjunctival small vessels Excoriation of skin suggesting severe pruritus Stigmata of prior arterial or venous thrombotic event Gouty arthritis Erythromelalgia

Diagnostic Criteria-First rule out Secondary Causes of Erythrocytosis : 

Diagnostic Criteria-First rule out Secondary Causes of Erythrocytosis

Diagnostic Criteria : 

Diagnostic Criteria Polycythemia Vera Study Group (1960s) Major Criteria Increased red cell mass: Males ≥ 36ml/kg, Females ≥ 32ml/kg Arterial oxygen saturation ≥ 92% Splenomegaly Minor Criteria Platelet count >400,000/microL WBC >12,000/microL Leukocyte alkaline phosphatase score >100 Vitamin B12 >900 pg/ml Requires all 3 major criteria or 2 major and 2 minor criteria BUT, there were significant limitations with these original criteria…

Problems with PVSG criteria : 

Problems with PVSG criteria Determination of red cell mass can be misleading if patient is obese as body fat is relatively avascular In addition many institutions do not have ability to calculate Felt that females with hgb >16.5 and males with hgb >18.5 have increased RCM making measurement not necessary Elevated LAP score is sensitive but not specific B12 studies are neither sensitive nor specific

Revised WHO criteria for PCV : 

Revised WHO criteria for PCV Major Hgb >18.5 in men, 16.5 g/dL in women Presence of JAK2 V617F or other functionally similar mutation Minor Bone marrow bx showing hypercellularity for age with trilineage growth with prominent erythroid, granulocytic, and megakaryocytic proliferation Serum erythropoietin level below nml reference range Endogenous erythroid colony formation in vitro Using vitro culture techniques, there is formation of erythroid colonies in absence of added erythropoietin

JAK2 mutation : 

JAK2 mutation Janus Kinase 2 (JAK2) has tyrosine kinase activity and is involved in signal transduction from EPOR (erythropoietin receptor) to nucleus for gene expression

JAK2 mutation : 

JAK2 mutation Single nucleotide JAK2 mutation (JAK2 V617F) Valine to phenylalanine substition at codon 617 Mutation occurs in pseudokinase (normally negative regulator of kinase activity) domain of JAK2 gene resulting in constitutively activated tyrosine kinase Exclusive to disorders of myeloid lineage and not observed in lymphoid neoplasms or solid tumors Mutation prevalence: PCV (60-90%), ET and Idiopathic Myelofibrosis (30-50%)

Treatment : 

Treatment Phlebotomy Goal is to reduce viscosity, reduce HCT to <45. Yielded best overall survival in initial PVSG trial from 1967-1987 But increased risk of thrombosis within 3 years leading to addition of low-dose aspirin

Treatment : 

Treatment Hydroxyurea Acts by non-alkalating mechanism to inhibit the enzyme ribonucleotide diphosphate reductase involved in DNA synthesis Reduced incidence of thrombosis compared to phlebotomy Effective in reducing blood counts although transient cytopenia may occur Some question of whether this drug has potential for being leukemogenic, although not proven

Treatment : 

Treatment Interferon alpha Wide range of biological actions including anti-proliferative and cellular differentiating effects Shown to provide relief from intractable pruritus and reduce spleen size Associated with significant side effects including influenza-like syndrome, pyrexia, myalgias, and athralgias Not shown to be teratogenic or cross placenta thus could be used in pregnancy

Potential Treatments : 

Potential Treatments Imatinib (Gleevec) Tyrosine kinase inhibitor which inhibits tyrosine kinase activity of BCR-ABL (remember CML) In vitro it inhibits autonomous growth of erythroid colonies in PCV Could this have similar effect on tyrosine kinase activity of JAK2?

References : 

References De Keersmaecker K, Cools J. Chronic myeloproliferative disorders: a tyrosine kinase tale. Leukemia 2006:20,200-205. Levine RL, Gilliland DG. JAK-2 mutations and their relevance to myeloproliferative disease. Curr Opin Hematol 2007:14;43-47. McMullin MF. A review of the therapeutic agents used in the management of polycythemia vera. Hematol Oncol 2007;25:58-65. Prchal JT. Molecular pathogenesis of congenital polycythemic disorders and polycythemia vera. UpToDate 2008. Stuart BJ, Viera AJ. Polycythemia Vera. Am Fam Physician 2004:69;2139-44. Tefferi A. Diagnostic approach to the patient with suspected polycythemia vera. UpToDate 2008. Tefferi A. Prognosis and treatment of polycythemia vera. UpToDate 2008.