What Are Thrombocythemia and Thrombocytosis?
Thrombocythemia (THROM-bo-si-THE-me-ah) and
thrombocytosis (THROM-bo-si-TO-sis) are conditions in which your blood has a
high number of blood cell fragments called platelets (PLATE-lets).
Platelets are made in your bone marrow along with
other kinds of blood cells. They travel through your blood vessels and stick
together (clot) to stop any bleeding that could happen if a blood vessel is
damaged. Platelets also are called thrombocytes (THROM-bo-sites), because a
clot also is called a thrombus.
A normal platelet count ranges from 150,000 to
450,000 platelets per microliter of blood.
The term "thrombocythemia" is preferred when the
cause of the high platelet count isn't known. The condition is then called
primary or essential thrombocythemia.
This condition occurs when faulty cells in the bone
marrow make too many platelets. Bone marrow is the sponge-like tissue inside
the bones. It contains stem cells that develop into red blood cells, white
blood cells, or platelets. What causes the bone marrow to make too many
platelets often isn't known.
With primary thrombocythemia, a high platelet count
may occur alone or with other blood cell disorders. The platelet count can be
as low as 500,000 platelets per microliter of blood or higher than 1 million
platelets per microliter of blood. This condition isn't common.
When another disease or condition causes a high
platelet count, the term "thrombocytosis" is preferred. This condition often is
called secondary or reactive thrombocytosis.
In this condition, the platelet count usually is
less than 1 million platelets per microliter of blood. Secondary thrombocytosis
is more common than primary thrombocythemia.
Most people who have a high platelet count don't
have signs or symptoms. Rarely, serious or life-threatening symptoms can
develop, such as blood clots and bleeding. These symptoms mostly occur in
people who have primary thrombocythemia.
People who have primary thrombocythemia but no signs
or symptoms don't need treatment, as long as the condition remains stable.
Other people who have this condition may need medicines or procedures to treat
it. Most people who have primary thrombocythemia will live a normal life
Treatment and outlook for secondary thrombocytosis
depend on its underlying cause.