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.
Overview
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.
Outlook
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.
Other Names for Thrombocythemia and
Thrombocytosis
Primary thrombocythemia also is called:
- Essential thrombocythemia. This term is used when
a high platelet count occurs alone (that is, without other blood cell
disorders).
- Idiopathic thrombocythemia.
- Primary or essential thrombocytosis. These are
less favored terms.
Secondary thrombocytosis also is known as:
- Reactive thrombocytosis.
- Secondary thrombocythemia. This is a less favored
term.
What Causes Thrombocythemia and
Thrombocytosis?
Primary Thrombocythemia
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.
("Inherited" means the condition is 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.
Secondary Thrombocytosis
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:
- Recovery from serious loss of blood
- Recovery from a very low platelet count caused by
excessive alcohol use and lack of vitamin B12 or folate
- Acute infection or inflammation
- Response to physical activity
Who Is At Risk for Thrombocythemia or
Thrombocytosis?
Primary Thrombocythemia
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.
Secondary Thrombocytosis
You may be at risk for secondary thrombocytosis if
you have a disease, condition, or factor that can cause it. (For more
information, see "What Causes Thrombocythemia and
Thrombocytosis?")
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.
What Are the Signs and Symptoms of Thrombocythemia
and Thrombocytosis?
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.
Primary Thrombocythemia
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.
Blood Clots
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:
- Changes in speech or awareness, ranging from
confusion to passing out
- Seizures
- Upper body discomfort in one or both arms, the
back, neck, jaw, or stomach
- Shortness of breath and nausea (feeling sick to
your stomach)
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
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
(lu-KE-me-ah). Leukemia is a cancer of the blood cells.
Secondary Thrombocytosis
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.
How Are Thrombocythemia and Thrombocytosis
Diagnosed?
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.
Medical History
Your doctor may ask you about factors that can
affect your platelets, such as:
- Any medical procedures or
blood
transfusions you've had
- Any recent infections or vaccinations you've
had
- The medicines you take, including
over-the-counter medicines
- Your general eating habits, including the amount
of alcohol you normally drink
- Any family history of high platelet counts
Physical Exam
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.
Diagnostic Tests
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.
Blood Smear
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 tests check whether your bone marrow is healthy. Blood cells,
including platelets, are made in bone marrow. The two bone marrow tests are
aspiration (as-pi-RA-shun) and biopsy.
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.
Other Tests
Your doctor may order other blood tests to look for
genetic factors that can cause a high platelet count.
How Are Thrombocythemia and Thrombocytosis
Treated?
Primary Thrombocythemia
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:
You will need to take these medicines throughout
your life.
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
(pal-pi-TA-shuns),
arrhythmias
(ah-RITH-me-ahs),
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
Plateletpheresis (PLATE-let-fe-REH-sis) 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
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.
How Can Thrombocythemia and Thrombocytosis Be
Prevented?
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 or 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.
Key Points
- Thrombocythemia and thrombocytosis are conditions
in which your blood has a high number of blood cell fragments called platelets.
Platelets travel through your blood vessels and stick together (clot) to stop
any bleeding that could happen if a blood vessel is damaged.
- 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. In this condition, faulty stem cells in
the bone marrow make too many platelets. In some cases, the condition is
inherited or caused by a genetic mutation.
- When another disease or condition causes a high
platelet count, the term "thrombocytosis" is preferred. This condition often is
called secondary or reactive thrombocytosis. Secondary thrombocytosis is more
common than primary thrombocythemia.
- Most people who have these conditions have no
signs or symptoms. In those who do, the most common symptoms are linked to
blood clots and bleeding. Symptoms include weakness, bleeding, headache, and
numbness of the hands and feet.
- People who have primary thrombocythemia are more
likely than those who have secondary thrombocytosis to have serious signs and
symptoms.
- Thrombocythemia and thrombocytosis are diagnosed
based on your medical history, a physical exam, and test results. Primary
thrombocythemia is diagnosed only after all other possible causes of a high
platelet count are ruled out.
- 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 form of the condition may need medicines or
procedures to treat it.
- Secondary thrombocytosis is treated by addressing
the underlying condition that's causing it.
- You can't prevent primary thrombocythemia. But,
you can take steps to reduce your risk for blood clots and prevent related
problems. Stop smoking and work to control your blood pressure and blood
cholesterol.
- You can't always prevent conditions that lead to
secondary thrombocytosis. However, if you have regular medical care, your
doctor may find these conditions before you develop a high platelet count.
- If you have thrombocythemia or thrombocytosis,
get regular medical care. Stop smoking and control risk factors for blood
clots. Watch for signs and symptoms of blood
clots and bleeding and report them to your doctor right away. Take all your
medicines as prescribed.
- Most people who have primary thrombocythemia will
live a normal lifespan. The outlook for secondary thrombocytosis depends on its
underlying cause.
Links to Other Information About Thrombocythemia
and Thrombocytosis
Non-NHLBI Resources
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