Thrombocytosis (throm-bo-sigh-TOE-sis) is a disorder in which your body produces too many platelets (thrombocytes), which play an important role in blood clotting. The disorder is called reactive thrombocytosis when it's caused by an underlying condition, such as an infection.
Thrombocytosis may also be caused by a blood and bone marrow disease. When caused by a bone marrow disorder, thrombocytosis is called autonomous, primary or essential thrombocytosis or essential thrombocythemia.
Your doctor may detect thrombocytosis in routine blood test results that show a high platelet level. If your blood test indicates thrombocytosis, it's important for your doctor to determine whether it's reactive thrombocytosis or if you have thrombocythemia, which is more likely to cause blood clots.
Reactive thrombocytosis rarely causes symptoms. More often, signs and symptoms relate to the underlying condition. If symptoms of reactive thrombocytosis do occur, they may include:
When to see a doctor
Bone marrow — spongy tissue inside your bones — contains stem cells that can give rise to red blood cells, white blood cells or platelets. Platelets travel through your blood vessels. They stick together to initiate clots that stop the bleeding when you damage a blood vessel, such as when you get a cut. A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood.
If you have thrombocytosis caused by a bone marrow disorder (essential thrombocythemia), your bone marrow overproduces the cells that form platelets (megakaryocytes), releasing too many platelets into your blood. If your blood test results reveal a high platelet count, it's important for your doctor to determine whether you have essential thrombocythemia or reactive thrombocytosis.
Reactive thrombocytosis causes include:
Medications that can cause reactive thrombocytosis include:
You may be at risk of thrombocytosis if you have a medical condition such as iron deficiency anemia or you've had surgery.
If your high platelet count results from a bone marrow disease (essential thrombocythemia), rather than reactive thrombocytosis, you may be at risk of developing blood clots, some of which can be life-threatening.
Preparing for your appointment
It's likely that a routine blood test showing a high platelet count will be your first indication that you have thrombocytosis.
Besides taking your medical history, examining you physically and running tests, your doctor may ask you about factors that could affect your platelets, such as any recent surgical procedures, blood transfusions or infections you've had. You may be referred to a doctor who specializes in blood diseases (hematologist).
Your doctor will look for what's causing your high platelet count, including determining whether it's reactive thrombocytosis due to an underlying condition or whether there's no apparent cause, which could indicate essential thrombocythemia or another bone marrow disorder.
Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be well prepared. Here's some information to help you get ready, and what to expect from your doctor.
What you can do
Your time with your doctor is limited, so preparing a list of questions will help you make the most of your time together. List your questions from most important to least important in case time runs out. For thrombocytosis, some basic questions to ask include:
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions that arise during your appointment.
Tests and diagnosis
You may find out you have thrombocytosis through one of the following tests:
Because a number of conditions can cause a temporary rise in your platelet count, your doctor likely will repeat the blood tests to see if your platelet count remains high over time.
A normal range for platelets is 150,000 to 450,000 platelets per microliter of blood. If your blood count is above 500,000, your doctor will likely look for an underlying condition. In most cases, signs and symptoms of the underlying condition help guide the diagnosis. Your doctor may also:
Treatments and drugs
Treatment for reactive thrombocytosis is directed at the underlying cause. If a recent surgery or an injury that caused significant blood loss is the cause, your elevated platelet count may not last long. If the cause is a chronic infection or an inflammatory disease, your platelet count may remain high until the condition is brought under control. In most cases, your platelet count will return to normal after the underlying cause is resolved.
Removal of your spleen may cause lifelong thrombocytosis. In that case, your doctor may prescribe low-dose aspirin to help prevent bleeding or blood-clotting incidents, although these occur rarely in reactive thrombocytosis.
Last Updated: 2010-07-16
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