Polycythemia vera

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Polycythemia vera
Classification and external resources
Polycythemia vera, blood smear.jpg
Blood smear from a patient with polycythemia vera
ICD-10D45
ICD-9238.4
ICD-O:M9950/3
MedlinePlus000589
MeSHD011087
 
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Polycythemia vera
Classification and external resources
Polycythemia vera, blood smear.jpg
Blood smear from a patient with polycythemia vera
ICD-10D45
ICD-9238.4
ICD-O:M9950/3
MedlinePlus000589
MeSHD011087

Polycythemia (or Polycythaemia, see spelling differences) vera (PV, PCV) (also known as erythremia, primary polycythemia and polycythemia rubra vera)[1] is a myeloproliferative blood cancer in which the bone marrow makes too many red blood cells.[1] It may also result in the overproduction of white blood cells and platelets.

Most of the health concerns associated with polycythemia vera are caused by the blood being thicker as a result of the increased red blood cells. It is more common in the elderly and may be symptomatic or asymptomatic. Common signs and symptoms include itching (pruritus), and severe burning pain in the hands or feet that is usually accompanied by a reddish or bluish coloration of the skin. Patients with polycythemia vera are more likely to have gouty arthritis. Treatment consists primarily of phlebotomy.

Epidemiology[edit]

Polycythemia veras occurs in all age groups,[2] although the incidence increases with age. One study found the median age at diagnosis to be 60 years,[3] while a Mayo Clinic study in Olmsted County, Minnesota found that the highest incidence was in people aged 70–79 years.[4] The overall incidence in the Minnesota population was 1.9 per 100,000 person-years, and the disease was more common in men than women.[4] A cluster around a toxic site was confirmed in northeast Pennsylvania in 2008. [5]

Pathophysiology[edit]

Polycythemia vera (PCV), being a primary polycythemia, is caused by neoplastic proliferation and maturation of erythroid, megakaryocytic and granulocytic elements to produce what is referred to as panmyelosis. In contrast to secondary polycythemias, PCV is associated with a low serum level of the hormone erythropoietin (EPO). Instead, PCV cells have a mutation in the tyrosine kinase (JAK2), which acts in signaling pathways of the EPO-receptor, rendering those cells hypersensitive to EPO.[6]

Symptoms[edit]

Erythromelalgia in a patient with longstanding polycythemia vera

Patients with polycythemia vera can be asymptomatic.[7] A classic symptom of polycythemia vera is pruritus or itching, particularly after exposure to warm water (such as when taking a bath),[8] which may be due to abnormal histamine release[9][10] or prostaglandin production.[11] Such itching is present in approximately 40% of patients with polycythemia vera.[3] Gouty arthritis may be present in up to 20% of patients.[3] Peptic ulcer disease is also common in patients with polycythemia vera; most likely due to increased histamine from mast cells, but may be related to an increased susceptibility to infection with the ulcer-causing bacterium H. pylori.[12] Another possible mechanism for the development for peptic ulcer is increased histamine release and gastric hyperacidity related with polycythemia vera.

A rare but classic symptom of polycythemia vera (and the related myeloproliferative disease essential thrombocythemia) is erythromelalgia.[13] This is a sudden, severe burning pain in the hands or feet, usually accompanied by a reddish or bluish coloration of the skin. Erythromelalgia is caused by an increased platelet count or increased platelet "stickiness" (aggregation), resulting in the formation of tiny blood clots in the vessels of the extremity; it responds rapidly to treatment with aspirin.[14][15]

Patients with polycythemia vera are prone to the development of blood clots (thrombosis). A major thrombotic complication (e.g. heart attack, stroke, deep venous thrombosis, or Budd-Chiari syndrome) may sometimes be the first symptom or indication that a person has polycythemia vera.

Headaches, lack of concentration and fatigue are common symptoms that occur in patients with polycythemia vera as well.

Diagnosis[edit]

Physical exam findings are non-specific, but may include enlarged liver or spleen, plethora, or gouty nodules. The diagnosis is often suspected on the basis of laboratory tests. Common findings include an elevated hemoglobin level and hematocrit, reflecting the increased number of red blood cells; the platelet count or white blood cell count may also be increased. The erythrocyte sedimentation rate (ESR) is decreased due to an increase in zeta potential. Because polycythemia vera results from an essential increase in erythrocyte production, patients have a low erythropoietin (EPO) level.

In primary polycythemia, there may be 8 to 9 million and occasionally 11 million erythrocytes per cubic millimeter of blood (a normal range for adults is 4-6), and the hematocrit may be as high as 70 to 80%. In addition, the total blood volume sometimes increases to as much as twice normal. The entire vascular system can become markedly engorged with blood, and circulation times for blood throughout the body can increase up to twice the normal value. The increased numbers of erythrocytes can cause the viscosity of the blood to increase as much as five times normal. Capillaries can become plugged by the very viscous blood, and the flow of blood through the vessels tends to be extremely sluggish.

As a consequence of the above, people with untreated polycythemia vera are at a risk of various thrombotic events (deep venous thrombosis, pulmonary embolism), heart attack and stroke, and have a substantial risk of Budd-Chiari syndrome (hepatic vein thrombosis),[16] or myelofibrosis. The condition is considered chronic; no cure exists. Symptomatic treatment (see below) can normalize the blood count and most patients can live a normal life for years.

The disease appears more common in Jews of European extraction than in most non-Jewish populations. Some familial forms of polycythemia vera are noted, but the mode of inheritance is not clear.

Recently, in 2005, a mutation in the JAK2 kinase (V617F) was found by multiple research groups [17][18] to be strongly associated with polycythemia vera. JAK2 is a member of the Janus kinase family and makes the erythroid precursors hypersensitive to erythropoietin (EPO). This mutation may be helpful in making a diagnosis or as a target for future therapy.

Treatment[edit]

Untreated, polycythemia vera can be fatal.[19][20] Research has found that the "1.5-3 years of median survival in the absence of therapy has been extended to at least 10-20 years because of new therapeutic tools."[21]

As the condition cannot be cured, treatment focuses on treating symptoms and reducing thrombotic complications by reducing the erythrocyte levels.

Bloodletting (called venesection or phlebotomy) is one form of treatment, which often may be combined with other therapies. The removal of blood from the body reduces the blood volume and brings down the hematocrit levels; in patients with polycythemia vera, this reduces the risk of blood clots. Venesection is typically performed in people with polycythemia vera to bring their hematocrit (red blood cell percentage) down below 45 for men or 42 for women.[22] It has been observed that phlebotomy also improves cognitive impairment.[23]

Low dose aspirin (75–81 mg daily) is often prescribed. Research has shown that aspirin reduces the risk for various thrombotic complications.

Chemotherapy for polycythemia may be used, either for maintenance, or when the rate of bloodlettings required to maintain normal hematocrit is not acceptable, or when there is significant thrombocytosis or intractable pruritus. This is usually with a "cytoreductive agent" (hydroxyurea, also known as hydroxycarbamide).

The tendency of some practitioners to avoid chemotherapy if possible, especially in young patients, is a result of research indicating possible increased risk of transformation to acute myelogenous leukemia (AML). While hydroxyurea is considered safer in this aspect, there is still some debate about its long-term safety.

In the past, injection of radioactive isotopes (principally phosphorus-32) was used as another means to suppress the bone marrow. Such treatment is now avoided due to a high rate of AML transformation.

Other therapies include interferon injections, and in cases where secondary thrombocytosis (high platelet count) is present, anagrelide may be prescribed.

Bone marrow transplants are rarely undertaken in polycythemia patients; since this condition is non-fatal if treated and monitored, the benefits rarely outweigh the risks involved in such a procedure.

There are indications that with certain genetic markers, erlotinib may be an additional treatment option for this condition.[24]

Selective JAK2 inhibitors are being investigated in vitro and in clinical trials.[25][26][27][28]

See also[edit]

References[edit]

  1. ^ a b "polycythemia vera." at Encyclopædia Britannica. 2010. Encyclopædia Britannica Online. 21 Sep. 2010
  2. ^ Passamonti F, Malabarba L, Orlandi E, Baratè C, Canevari A, Brusamolino E, Bonfichi M, Arcaini L, Caberlon S, Pascutto C, Lazzarino M (2003). "Polycythemia vera in young patients: a study on the long-term risk of thrombosis, myelofibrosis and leukemia". Haematologica 88 (1): 13–8. PMID 12551821. 
  3. ^ a b c Berlin NI (1975). "Diagnosis and classification of polycythemias". Semin Hematol 12: 339. 
  4. ^ a b Anía B, Suman V, Sobell J, Codd M, Silverstein M, Melton L (1994). "Trends in the incidence of polycythemia vera among Olmsted County, Minnesota residents, 1935-1989". Am J Hematol 47 (2): 89–93. doi:10.1002/ajh.2830470205. PMID 8092146. 
  5. ^ MICHAEL RUBINKAM (2008). "Cancer cluster confirmed in northeast Pennsylvania". Associated Press. [dead link]
  6. ^ Kumar, et al.: Robbin's Basic Pathology, 8th edition, Saunders, 2007
  7. ^ [Polycythemia vera EBSCO database] verified by URAC; accessed from Mount Sinai Hospital, New York
  8. ^ Saini KS, Patnaik MM, Tefferi A (2010). "Polycythemia vera-associated pruritus and its management". Eur J Clin Invest 40 (9): 828–34. doi:10.1111/j.1365-2362.2010.02334.x. PMID 20597963. 
  9. ^ Steinman H, Kobza-Black A, Lotti T, Brunetti L, Panconesi E, Greaves M (1987). "Polycythaemia rubra vera and water-induced pruritus: blood histamine levels and cutaneous fibrinolytic activity before and after water challenge". Br J Dermatol 116 (3): 329–33. doi:10.1111/j.1365-2133.1987.tb05846.x. PMID 3567071. 
  10. ^ Jackson N, Burt D, Crocker J, Boughton B (1987). "Skin mast cells in polycythaemia vera: relationship to the pathogenesis and treatment of pruritus". Br J Dermatol 116 (1): 21–9. doi:10.1111/j.1365-2133.1987.tb05787.x. PMID 3814512. 
  11. ^ Fjellner B, Hägermark O (1979). "Pruritus in polycythemia vera: treatment with aspirin and possibility of platelet involvement". Acta Derm Venereol 59 (6): 505–12. PMID 94209. 
  12. ^ Torgano G, Mandelli C, Massaro P, Abbiati C, Ponzetto A, Bertinieri G, Bogetto S, Terruzzi E, de Franchis R (2002). "Gastroduodenal lesions in polycythaemia vera: frequency and role of Helicobacter pylori". Br J Haematol 117 (1): 198–202. doi:10.1046/j.1365-2141.2002.03380.x. PMID 11918555. 
  13. ^ van Genderen P, Michiels J (1997). "Erythromelalgia: a pathognomonic microvascular thrombotic complication in essential thrombocythemia and polycythemia vera". Semin Thromb Hemost 23 (4): 357–63. doi:10.1055/s-2007-996109. PMID 9263352. 
  14. ^ Michiels J (1997). "Erythromelalgia and vascular complications in polycythemia vera". Semin Thromb Hemost 23 (5): 441–54. doi:10.1055/s-2007-996121. PMID 9387203. 
  15. ^ Landolfi R, Ciabattoni G, Patrignani P, Castellana M, Pogliani E, Bizzi B, Patrono C (1992). "Increased thromboxane biosynthesis in patients with polycythemia vera: evidence for aspirin-suppressible platelet activation in vivo". Blood 80 (8): 1965–71. PMID 1327286. 
  16. ^ Thurmes PJ, Steensma DP (July 2006). "Elevated serum erythropoietin levels in patients with Budd-Chiari syndrome secondary to polycythemia vera: clinical implications for the role of JAK2 mutation analysis". Eur. J. Haematol. 77 (1): 57–60. doi:10.1111/j.1600-0609.2006.00667.x. PMID 16827884. 
  17. ^ Baxter EJ, Scott LM, Campbell PJ, East C, Fourouclas N, Swanton S, Vassiliou GS, Bench AJ, Boyd EM, Curtin N, Scott MA, Erber WN, Green AR (2005). "Acquired mutation of the tyrosine kinase JAK2 in human myeloproliferative disorders". Lancet 365 (9464): 1054–61. doi:10.1016/S0140-6736(05)71142-9. PMID 15781101. 
  18. ^ Levine RL, Wadleigh M, Cools J, Ebert BL, Wernig G, Huntly BJ, Boggon TJ, Wlodarska I, Clark JJ, Moore S, Adelsperger J, Koo S, Lee JC, Gabriel S, Mercher T, D'Andrea A, Frohling S, Dohner K, Marynen P, Vandenberghe P, Mesa RA, Tefferi A, Griffin JD, Eck MJ, Sellers WR, Meyerson M, Golub TR, Lee SJ, Gilliland DG (2005). "Activating mutation in the tyrosine kinase JAK2 in polycythemia vera, essential thrombocythemia, and myeloid metaplasia with myelofibrosis". Cancer Cell 7 (4): 387–97. doi:10.1016/j.ccr.2005.03.023. PMID 15837627. 
  19. ^ Mayo Clinic staff. "Polycythemia vera - MayoClinic.com". Polycythemia vera: Definition. Mayo Clinic. Retrieved 2011-09-03. 
  20. ^ "What Is Polycythemia Vera?". What Is Polycythemia Vera?. National Heart, Lung and Blood Institute. Retrieved 2011-09-03. 
  21. ^ "Polycythemia Vera Follow-up". Polycythemia Vera Follow-up. Retrieved 2011-09-03. 
  22. ^ Streiff MB, Smith B, Spivak JL (2002). "The diagnosis and management of polycythemia vera in the era since the Polycythemia Vera Study Group: a survey of American Society of Hematology members' practice patterns". Blood 99 (4): 1144–9. doi:10.1182/blood.V99.4.1144. PMID 11830459. 
  23. ^ Di Pollina L, Mulligan R, Juillerat Van der Linden A, Michel JP, Gold G (2000). "Cognitive impairment in polycythemia vera: partial reversibility upon lowering of the hematocrit". Eur. Neurol. 44 (1): 57–9. PMID 10894997. 
  24. ^ Li Z, Xu M, Xing S, Ho W, Ishii T, Li Q, Fu X, Zhao Z (2007). "Erlotinib Effectively Inhibits JAK2V617F Activity and Polycythemia Vera Cell Growth". J Biol Chem 282 (6): 3428–32. doi:10.1074/jbc.C600277200. PMC 2096634. PMID 17178722. 
  25. ^ Open Label INCB018424 in Patients With Myelofibrosis and Post Polycythemia Vera/Essential Thrombocythemia Myelofibrosis. ClinicalTrials.gov.
  26. ^ Verstovsek S, Manshouri T, Quintás-Cardama A, et al. (February 2008). "WP1066, a novel JAK2 inhibitor, suppresses proliferation and induces apoptosis in erythroid human cells carrying the JAK2 V617F mutation". Clin. Cancer Res. 14 (3): 788–96. doi:10.1158/1078-0432.CCR-07-0524. PMID 18245540. 
  27. ^ Wernig G, Kharas MG, Okabe R, et al. (April 2008). "Efficacy of TG101348, a selective JAK2 inhibitor, in treatment of a murine model of JAK2V617F-induced polycythemia vera". Cancer Cell 13 (4): 311–20. doi:10.1016/j.ccr.2008.02.009. PMID 18394554. 
  28. ^ Geron I, Abrahamsson AE, Barroga CF, et al. (April 2008). "Selective inhibition of JAK2-driven erythroid differentiation of polycythemia vera progenitors". Cancer Cell 13 (4): 321–30. doi:10.1016/j.ccr.2008.02.017. PMID 18394555. 

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