thrombocythemia and thrombocytosis
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, 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
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 span.
Treatment and outlook for secondary thrombocytosis depend on its underlying cause.
In this condition, faulty stem cells in the bone marrow make too many platelets. What causes this to happen usually isn't known. When this process occurs without affecting other blood cells, it's called essential thrombocythemia.
A rare form of thrombocythemia is inherited, i.e., passed from parents to children.) In some cases, a genetic mutation may cause the condition.
In primary thrombocythemia, the platelets aren't normal. They may form blood clots, or, surprisingly, cause bleeding when they don't work properly.
Bleeding also can occur because of a condition that develops called von Willebrand disease. This condition affects the blood clotting process.
After many years, scarring of the bone marrow can occur.
This condition occurs when another disease, condition, or outside factor causes the platelet count to rise. For example, 35 percent of people who have high platelet counts also have cancer – mostly lung, gastrointestinal, breast, ovarian, and lymphoma. Sometimes a high platelet count is the first sign of cancer.
Unlike primary thrombocythemia, the platelets in secondary thrombocytosis usually are normal.
Conditions or factors that can cause a high platelet count are:
Some conditions can lead to a high platelet count that lasts for only a short time. These include:
Who is at risk?
This condition isn't common. The exact number of people who have the condition isn't known. Some estimates suggest that 1 to 2.5 out of every 100,000 people have primary thrombocythemia. This number may be low, because most people who have the condition don't have symptoms. Therefore, they may not know they have it.
Primary thrombocythemia occurs mostly between the ages of 50 and 70, but it can occur at any age. For unknown reasons, a higher number of women around the age of 30 have primary thrombocythemia than men of the same age.
You may be at risk for secondary thrombocytosis if you have a disease, condition, or factor that can cause it.
This condition is more common than primary thrombocythemia. In two studies of people with high platelet levels, most people with platelet counts over 500,000 had secondary thrombocytosis.
Signs and symptoms
Most people who have thrombocythemia or thrombocytosis have no signs or symptoms. These conditions often are discovered only after routine blood tests.
People who have primary thrombocythemia are more likely than those who have secondary thrombocytosis to have serious signs and symptoms.
Often, people who have symptoms of primary thrombocythemia only have a mild form of the condition. The most common symptoms are linked to blood clots and bleeding. They are weakness, bleeding, headache, and numbness of the hands and feet.
In primary thrombocythemia, blood clots most often develop in the brain, hands, and feet. But they can happen anywhere in the body, including in the heart and intestines.
Blood clots in the brain cause symptoms in 25 percent of people who have this condition. Common symptoms are chronic (ongoing) headache and dizziness. In extreme cases, stroke may occur.
Blood clots in the tiny blood vessels of the hands and feet leave them numb and red. This may lead to an intense burning and throbbing pain felt mainly on the palms of the hands and the soles of the feet.
Other signs and symptoms of blood clots may include:
Blood clots in the placenta cause fetal death or miscarriage in half of pregnant women who have primary thrombocythemia.
Blood clots aren't only linked to having thrombocythemia or thrombocytosis, but to other factors as well. Age (being older than 60), prior blood clots, diabetes, high blood pressure, and smoking also increase your risk for blood clots.
Bleeding most often occurs in people who have platelet counts higher than 1 million platelets per microliter of blood. Signs of bleeding include nosebleeds, bruising, bleeding from the mouth or gums, or blood in the stools.
Although bleeding usually is linked to having a low platelet count, it also can occur in people who have high platelet counts. Blood clots that develop in thrombocythemia or thrombocytosis may use up your body's platelets. This means that not enough platelets are left in your bloodstream to seal off any cuts and breaks in the blood vessels.
Another cause of bleeding in patients who have very high platelets counts is a condition called von Willebrand Disease. This condition affects the blood clotting process.
In rare cases of primary thrombocythemia (less than 2 percent), the faulty bone marrow cells will cause a form of leukemia (a cancer of the blood cells).
People who have secondary thrombocytosis have a lower risk for bleeding and blood clots. This is because their platelets are generally normal (unlike in primary thrombocythemia) and their platelet counts aren't as high.
However, people who have this condition are at higher risk for blood clots and bleeding if they're on bed rest or have a severe disease of the arteries.
Your doctor will diagnose thrombocythemia or thrombocytosis based on your medical history, a physical exam, and test results. A hematologist also may be involved in your care. This is a doctor who treats people who have blood diseases.
Your doctor may ask you about factors that can affect your platelets, such as:
Your doctor will do a physical exam to look for signs and symptoms of bleeding and blood clots. He or she also will check for signs of conditions that can cause secondary thrombocytosis, such as infection.
Primary thrombocythemia is diagnosed only after all other possible causes of a high platelet count are ruled out. For example, your doctor may order tests to check for early, undiagnosed cancer. If another disease, condition, or factor is causing a high platelet count, the diagnosis is secondary thrombocytosis.
Your doctor may order one or more of the following tests to help diagnose a high platelet count.
Complete blood count
A complete blood count (CBC) measures the levels of red blood cells, white blood cells, and platelets in your blood. For this test, a small amount of blood is drawn from a blood vessel, usually in your arm.
If you have thrombocythemia or thrombocytosis, the test results will show that your platelet count is high.
A blood smear is used to check the condition of your platelets. For this test, a small amount of blood is drawn from a blood vessel, usually in your arm. Your doctor looks at the blood sample under a microscope.
Bone marrow tests
Bone marrow aspiration may be done to find out whether your bone marrow is making too many platelets. For this test, your doctor removes a small amount of fluid bone marrow through a needle. He or she examines the sample under a microscope to check for faulty cells.
A bone marrow biopsy often is done right after an aspiration. For this test, your doctor removes a small amount of bone marrow tissue through a needle. He or she examines the tissue to check the number and types of cells in the bone marrow. With thrombocythemia and thrombocytosis, the bone marrow has a higher than normal number of the very large cells that make platelets.
Your doctor may order other blood tests to look for genetic factors that can cause a high platelet count.
This condition is considered less harmful today than in the past, and its outlook is often good. People who have no signs or symptoms don't need treatment, as long as the condition remains stable.
Taking aspirin may help people who are at risk for blood clots, because aspirin thins the blood. However, you should talk to your doctor about using aspirin, because it can cause bleeding. Doctors prescribe aspirin to most pregnant women who have primary thrombocythemia. This is because it doesn't have a high risk for side effects to the fetus.
Some people who have primary thrombocythemia may need medicines or medical procedures to lower their platelet counts.
Medicines to lower platelet counts
You may need medicines to lower your platelet count if you:
Hydroxyurea. This is the most common platelet-lowering medicine to treat primary thrombocythemia. Hydroxyurea is used to treat cancers and other life-threatening diseases. It's most often given under the care of doctors who specialize in cancer or blood diseases. Patients on hydroxyurea are closely monitored.
Currently, hydroxyurea plus aspirin is the standard treatment for people who have primary thrombocythemia and are at high risk for blood clots.
Anagrelide. This medicine has been used to treat thrombocythemia. However, it seems less effective than hydroxyurea. Anagrelide also has side effects such as fluid retention, palpitations, arrhythmias, heart failure, and headaches.
Interferon alfa. This medicine is effective at lowering platelet counts. However, 20 percent of patients can't handle its side effects. These include a flu-like feeling, decreased appetite, nausea (feeling sick to the stomach), diarrhea, seizures, irritability, and sleepiness.
Doctors may prescribe this medicine to pregnant women who have primary thrombocythemia. This is because it's safer for the fetus than hydroxyurea and anagrelide.
Plateletpheresis is a procedure used to rapidly lower your platelet count. This procedure is only used for emergencies. For example, if you're having a stroke due to primary thrombocythemia, you may need plateletpheresis.
During this procedure, an intravenous (IV) needle that's connected to a tube is placed in one of your blood vessels to remove blood. The blood goes through a machine that removes platelets from the blood. The remaining blood is then put back into you through an IV line in one of your blood vessels.
One or two procedures may be enough to reduce your platelet count to a safe level.
Secondary thrombocytosis is treated by addressing the underlying condition that's causing it.
People who have this condition usually don't need platelet-lowering medicines or procedures. This is because their platelets are generally normal (unlike in primary thrombocythemia). Also, their platelet counts often aren't high enough to put them at risk for blood clots or bleeding.
You can't prevent primary thrombocythemia. However, you can take steps to reduce your risk for blood clots and prevent related problems.
Age, prior blood clots, diabetes, high blood pressure, high blood cholesterol, and smoking are all risk factors for blood clots. To reduce your risk, stop smoking and work to control the risk factors that you can.
It's not always possible to prevent conditions that lead to secondary thrombocytosis. But, if you have regular medical care, your doctor may find these conditions before you develop a high platelet count.
Living with thrombocythemia and thrombocytosis
If you have thrombocythemia or thrombocytosis, it's important to:
If you're taking medicines to lower your platelet count, tell your doctor or dentist about them before any surgical or dental procedures. These medicines thin your blood and may increase bleeding during such procedures.
Medicines that thin the blood also may cause internal bleeding. Signs of internal bleeding include bruises, bloody or tarry-looking stools, pink or bloody urine, increased menstrual bleeding, bleeding gums, and nosebleeds. Contact your doctor right away if you have any of these signs.
Avoid over-the-counter pain medicines such as ibuprofen (except Tylenol®). These medicines may raise your risk for bleeding in the stomach or intestines and may limit the effect of aspirin. Be aware that cold and pain medicines and other over-the-counter remedies may contain ibuprofen.