Polycythemia
From Wikipedia, the free encyclopedia
| ICD-10 | D45. (ICD-O 9950/3), D75.1, P61.1 |
|---|---|
| ICD-9 | 238.4, 289.0, 776.4 |
Polycythemia is a condition in which there is a net increase in the total number of red blood cells in the body. The overproduction of red blood cells may be due to a primary process in the bone marrow (a so-called myeloproliferative syndrome), or it may be a reaction to chronically low oxygen levels or, rarely, a malignancy.
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[edit] Primary polycythemia (Polycythemia vera)
Primary polycythemia, often called polycythemia vera (PCV), polycythemia rubra vera (PRV), or erythremia, occurs when excess red blood cells are produced as a result of an abnormality of the bone marrow. Often, excess white blood cells and platelets are also produced. Polycythemia vera is classified as a myeloproliferative disease.
[edit] Epidemiology
Polycythemia vera occurs in all age groups (including children),[1] although the incidence increases with age. One study found the median age at diagnosis to be 60 years,[2] while a study in Olmsted County, Minnesota found that the highest incidence was in people aged 70-79 years.[3] 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.[3]
[edit] Symptoms
Patients with polycythemia vera are often asymptomatic. A classic symptom of polycythemia vera is generalized itching, particularly after exposure to warm water, which may be due to abnormal histamine release[4][5] or prostaglandin production.[6] Such itching is present in approximately 40% of patients with polycythemia vera.[2] Gouty arthritis may be present in up to 20% of patients.[2] Peptic ulcer disease is also common in patients with polycythemia vera; the reasons for this are unclear, but may be related to an increased susceptibility to infection with the ulcer-causing bacterium H. pylori.[7]
A rare but classic symptom of polycythemia vera (and the related myeloproliferative disease essential thrombocythemia) is erythromelalgia.[8] 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", resulting in the formation of tiny blood clots in the vessels of the extremity; it responds rapidly to treatment with aspirin.[9][10]
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.
[edit] Diagnosis
Patients with polycythemia vera may often be asymptomatic. 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 or hematocrit, reflecting the increased number of red blood cells; the platelet count or white blood cell count may also be increased, low erythropoietin (EPO) level, and normal oxygen saturation > 92%.
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 increase 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.
Recently, in 2005, a mutation in the JAK2 kinase (V617F) was found by multiple research groups (Baxter et al., 2005; Levine et al., 2005) to be strongly associated with polycythemia vera. JAK2 is a member of the Janus kinase family. This mutation may be helpful in making a diagnosis or as a target for future therapy.
As a consequence of the above, people with untreated PV 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). 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.
[edit] Secondary polycythemia
Secondary polycythemia is caused by either natural or artificial increases in the production of erythropoietin that result in an increased production of erythrocytes. In secondary polycythemia, there may be 6 to 8 million and occasionally 9 million erythrocytes per cubic millimeter of blood. A type of secondary polycythemia in which the production of erythropoietin increases appropriately is called physiologic polycythemia. Physiologic polycythemia occurs in individuals living at high altitudes, where oxygen availability is less than at sea level. Many athletes train at higher altitudes to take advantage of this effect — a legal form of blood doping. Actual polychthemia sufferers have been known to use their condition as an athletic advantage for greater stamina.
Other causes of secondary polycythemia include smoking, renal or liver tumors, or heart or lung diseases that result in hypoxia. Endocrine abnormalities, prominently including pheochromocytoma and adrenal adenoma with Cushing's syndrome are also secondary causes. Athletes and bodybuilders who abuse anabolic steroids or erythropoietin may develop secondary polycythemia.
[edit] Relative polycythemia
Relative polycythemia is an apparent rise of the erythrocyte level in the blood; however, the underlying cause is reduced blood plasma. Relative polycythemia is often caused by fluid loss eg. burns, dehydration and stress polycythemia.
[edit] Treatment
As the condition cannot be cured, treatment focuses on treating symptoms and reducing thrombotic complications reducing the erythrocyte levels.
Bloodletting 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.
Low dose aspirin is often prescribed. Research has shown that aspirin reduces the risk for various thrombotic complications.
Chemotherapy for polycythemia may be used sparingly, when the rate of bloodlettings required to maintain normal hematocrit is not acceptable. This is usually with a "cytoreductive agent" (hydroxyurea, also known as hydroxycarbamide).
The tendency to avoid chemotherapy if possible, especially in young patients, is due to research indicating increased risk of transformation to AML, and 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 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.
[edit] References
- ^ 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.
- ^ a b c Berlin, NI. Diagnosis and classification of polycythemias. Semin Hematol 1975; 12:339.
- ^ 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. PMID 8092146.
- ^ 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. PMID 3567071.
- ^ 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. PMID 3814512.
- ^ 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.
- ^ 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. PMID 11918555.
- ^ 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. PMID 9263352.
- ^ Michiels J (1997). "Erythromelalgia and vascular complications in polycythemia vera.". Semin Thromb Hemost 23 (5): 441-54. PMID 9387203.
- ^ 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.
- 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. PMID 15781101.
- 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. PMID 15837627.
