Essential Thrombocythemia

Alternative names: ET, Essential Thrombocytosis, Essential Thrombocythaemia, Primary Thrombocytosis

Essential thrombocythemia is a rare chronic blood disorder characterized by the overproduction of platelets in the bone marrow.  It is a slowly-progressing disorder with long symptom-free periods punctuated by thrombotic or hemorrhagic events.

Incidence

The incidence of ET is between 6 and 25 cases per million people per year.  People older than 60 are most likely to develop the condition, though 20% of those with this condition are under 40.  The median age at onset is 65-70.  Women are 1.5 times more likely than men to develop the condition.

There is evidence that exposure to chemicals or to electrical wiring may increase a person's risk for the condition.

Signs and Symptoms

Most ET patents show no symptoms; the condition is usually discovered during routine blood work.  Where symptoms are present, they may include:

• Heart attack or stoke
• Bleeding
• Blood clots
• Bruising
• Elevated white blood cell count
• Reduced red blood cell count
• Headache
• Nausea
• Vomiting
• Gastrointestinal bleeding
• Blood in the urine
• Abdominal pain
• Visual disturbances
• Dizziness
• Fainting
• Enlarged spleen
• Numbness in the extremities
• Burning or throbbing pain, redness, and swelling of the hands and feet

Treatment and Prevention

Not all those affected will require aggressive treatment.  Based on their age, medical history, blood counts and lifestyles, patients are classed as either low or high risk for bleeding/blood clotting.  Those with low risk are usually treated with low-dose aspirin (for headache and burning pain in the skin); those at high risk are given hydroxycarbamide and/or other treatments that reduce platelet count such as Hydroxyurea (Droxia, Hydrea), interferon-a and anagrelide (Agrylin), as well as aminocaproic acid to reduce bleeding.

Prognosis; Complications

Well-documented medical regimens can reduce and control the number of platelets, which reduces the risk of thrombotic or hemorrhagic events.  A well-controlled ET patient can have a normal lifespan.

Rarely, ET may develop into acute myeloid leukemia (AML) or myelofibrosis.