Find information on thousands of medical conditions and prescription drugs.

Essential thrombocythemia

Essential thrombocytosis (ET, essential thrombocythemia) is a rare and chronic blood disorder characterized by the overproduction of megakaryocytes (the precursor cell for platelets). Most of these patients will have platelet counts over 600,000 per cubic mm. In some cases this disorder may be progressive, and (very rarely) evolves into acute leukemia or myelofibrosis. more...

Home
Diseases
A
B
C
D
E
Ebola hemorrhagic fever
Ebstein's anomaly
Eclampsia
Ectodermal Dysplasia
Ectopic pregnancy
Ectrodactyly
Edwards syndrome
Ehlers-Danlos syndrome
Ehrlichiosis
Eisoptrophobia
Elective mutism
Electrophobia
Elephantiasis
Ellis-Van Creveld syndrome
Emetophobia
Emphysema
Encephalitis
Encephalitis lethargica
Encephalocele
Encephalomyelitis
Encephalomyelitis, Myalgic
Endocarditis
Endocarditis, infective
Endometriosis
Endomyocardial fibrosis
Enetophobia
Enterobiasis
Eosinophilia-myalgia...
Eosinophilic fasciitis
Eosophobia
Ependymoma
Epicondylitis
Epidermolysis bullosa
Epidermolytic hyperkeratosis
Epididymitis
Epilepsy
Epiphyseal stippling...
Epistaxiophobia
EPP (erythropoietic...
Epstein barr virus...
Equinophobia
Ergophobia
Erysipelas
Erythema multiforme
Erythermalgia
Erythroblastopenia
Erythromelalgia
Erythroplakia
Erythropoietic...
Esophageal atresia
Esophageal varices
Esotropia
Essential hypertension
Essential thrombocythemia
Essential thrombocytopenia
Essential thrombocytosis
Euphobia
Evan's syndrome
Ewing's Sarcoma
Exencephaly
Exophthalmos
Exostoses
Exploding head syndrome
Hereditary Multiple...
Hereditary Multiple...
Hereditary Multiple...
Hereditary Multiple...
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Medicines

Pathophysiology

The pathologic basis for this disease is unknown. However, essential thrombosis resembles polycythemia vera in that cells of the megakaryocytic series are more sensitive to growth factors. Platelets derived from the abnormal megakaryocytes do not function properly, which contributes to the clinical features of bleeding and thrombosis.

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 associated with essential thrombocytosis. JAK2 is a member of the Janus kinase family. This mutation be helpful in making a diagnosis or as a target for future therapy.

Clinical findings and symptoms

Essential thrombocytosis is the most rare of the myeloproliferative family of diseases. The major symptoms are bleeding and thrombosis. Other symptoms include an enlarged spleen (splenomegaly), epistaxis (nosebleeds) and bleeding from gums and gastrointestinal tract. One characteristic symptom is throbbing and burning of the hands and feet due to the occlusion of small arterioles by platelets (erythromelalgia).

Clinical course

Essential thrombocytosis is a slowly progressing disorder with long asymptomatic periods punctuated by thrombotic or hemorrhagic crises. It is diagnosed at a rate of about 2 to 3 per 100,000 individuals and usually affects middle aged to elderly individuals (although it can affect children and young adults). The median survival time for patients with this disorder is 12 to 15 years.

Treatment

In cases where patients have life-threatening complications, the platelet count can be reduced rapidly through platelet apheresis (a procedure that removes platelets from the blood directly). Long-term decreases in platelet counts can reduce bleeding and clotting complications. Common medications include hydroxyurea, interferon-alpha, or anagrelide. Aspirin may also help decrease clotting.

Read more at Wikipedia.org


[List your site here Free!]


Polycythemia Vera and Essential Thrombocythemia
From American Family Physician, 2/15/01 by Grace Brooke Huffman

Polycythemia vera and essential thrombocythemia are chronic myeloproliferative diseases. The main goal of treatment in patients with these conditions is to prevent thrombohemorrhagic complications. Tefferi and colleagues reviewed the medical literature to summarize the pathogenesis, diagnosis and treatment of polycythemia vera and essential thrombocythemia.

Polycythemia vera can be diagnosed when a patient has all three major criteria (i.e., increased red blood cell mass [at least 36 mL per kg for men, at least 32 mL per kg for women]; normal arterial oxygen saturation [at least 92 percent]; and splenomegaly) or the first two major criteria plus any two of the minor criteria (i.e., platelet count of more than 400 3 103 per [micro]L [400 3 109 per L]; leukocyte count of more than 12 3 103 per [micro]L [.01 3 109 per L]; alkaline phosphatase level of more than 100 U per L; a vitamin B12 level of more than 900 pg per mL [664 pmol per L] or an unbound vitamin B12 binding capacity of more than 2,200 pg per mL [1,623 pmol per L]).

Men are more often affected by polycythemia vera than women, and about one fifth of patients present with a thrombotic event. Bleeding complications occur less frequently than thrombotic complications but are more likely in patients who are taking nonsteroidal anti-inflammatory agents. Other symptoms of polycythemia vera include headaches, transient neurologic or ocular complaints, and paresthesias. Pruritus after bathing may also occur. The risk of thrombosis does not correlate with the degree of thrombocytosis or the level of platelet function, although the number of patients analyzed in studies may not be large enough to show a correlation.

When phlebotomy was the sole treatment of polycythemia vera, the average rate of survival was extended to more than 12 years. Adding chlorambucil therapy to phlebotomy decreased the rate of survival to about nine years. Similarly, radioactive phosphorus plus phlebotomy decreased the rate of survival to less than 11 years. Patients who received these medications also had a higher risk of acquiring acute leukemia than those being treated with phlebotomy alone. However, chlorambucil and radioactive phosphorus were associated with a lower risk of thrombosis than treatment with phlebotomy alone. Patients taking hydroxyurea had lower incidences of early thrombosis and acute leukemia. Based on this information, the authors recommend that all patients with polycythemia vera be treated with phlebotomy (with goal hematocrit levels of less than 45 percent [0.45] in men and 42 percent [0.42] in women); patients at high risk for thrombosis should also receive hydroxyurea.

Essential thrombocythemia is diagnosed after reactive and clonal thrombocytosis are excluded. This can be done by measuring C-reactive protein levels, erythrocyte sedimentation rates and fibrinogen levels. A bone marrow biopsy can rule out other chronic myeloid disorders. Women have essential thrombocythemia more often than men. Vasomotor symptoms such as headaches and paresthesias are more common, while thrombotic and bleeding events are progressively less common. There is a low incidence of transformation into acute leukemia or myelofibrosis with myeloid metaplasia. Prognosis is worse in patients older than 60 years and those who have a history of thrombosis. Qualitative or quantitative platelet abnormalities are not consistent predictors of thrombosis risk, although extreme thrombocytosis may be related to a higher incidence of gastrointestinal tract hemorrhage. The risk of thrombosis is reduced by the use of hydroxyurea (from 24 percent to less than 4 percent) and by keeping the platelet count less than 400 3 103 per [micro]L (400 3 109 per L).

In patients with polycythemia vera or essential thrombocythemia, vasomotor symptoms can be relieved with low-dose aspirin therapy (75 to 100 mg per day). However, use of aspirin should be avoided in patients with bleeding diathesis. The authors conclude that treatment of polycythemia vera or essential thrombocythemia should be directed by the presence of risk factors for thrombohemorrhagic complications. Treatment approaches for these disorders are outlined in Tables 1 and 2 on page 746.

COPYRIGHT 2001 American Academy of Family Physicians
COPYRIGHT 2001 Gale Group

Return to Essential thrombocythemia
Home Contact Resources Exchange Links ebay