Idiopathic Thrombocytopenic Purpura (ITP)

Understanding platelets

Platelets are tiny particles in the blood and help blood to clot when we cut or injure ourselves. They are produced inside bone, in the bone marrow. They are then released in the bloodstream and travel through the body for about seven days before they are removed by the spleen. The spleen is an organ that lies at the top of the abdomen under the left ribs.

A normal number of platelets in a blood test is between 150 and 400 x 10⁹ per litre. If you have too many platelets, your blood will clot too easily. If you do not have enough platelets, you may bruise and bleed more easily.

What is ITP?

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease involving platelets. Autoimmune disorders are when the body produces a protein (antibody) that attaches itself to, and damages, another part of the body. In ITP, the antibodies are produced against platelets. Once the antibodies have attached to platelets, the platelets do not work as well. They are also removed more quickly by the spleen because they are abnormal.

• Idiopathic means that there is no detectable underlying cause yet found.
• Thrombocytopenic means not enough platelets (thrombocyte is another name for platelet).
• Purpura is a purple-red rash over the body.

Although the cause of ITP is not clear, it is known to be something to do with the immune system. Therefore the disease is increasingly being called 'immune thrombocytopenic purpura' - which is still shortened to ITP.

ITP is quite different in children and adults and should be considered separately.

ITP IN CHILDREN

How common is ITP in children?

ITP occurs in about 5 in 100,000 children. It is three times more common in girls than in boys.

What are the symptoms?

• Most children will not have any symptoms.
• Those that do develop symptoms have bruising and purpura, and some have bleeding such as nose bleeds. It usually appears quickly, over 1-2 days. The condition often occurs about 2-3 weeks following an infection (often a common viral infection), or occasionally following an immunisation. The symptoms disappear over 6-8 weeks in most cases.
• Very occasionally, it may cause severe bleeding which requires emergency treatment.
• The platelet levels in about 1 in 10 affected children does not ever return to normal which means that they have developed chronic (persistent) ITP.

So, what seems to happen in children with ITP is that the immune system is triggered to produce antibodies against the platelets by an infecting virus or other germ. In most cases, this is a temporary 'immune reaction' that lasts several weeks only, and then symptoms go. But, in a minority of cases, once the immune reaction is triggered, the immune system continues to be faulty and the condition persists into chronic ITP.

How is ITP diagnosed?

ITP is diagnosed by a blood test called a full blood count. This test shows that there are less platelets than normal. The laboratory will also have a look at the blood under a microscope.

Sometimes other tests will be needed to make sure that the low number of platelets is not due to something else. (There are various other causes of a reduced number of platelets.) Rarely, this involves taking a sample of bone marrow.

What is the treatment?

Most children will not need any treatment, even if the number of platelets is very low. The decision to treat is usually based on whether your child has serious bleeding or very pronounced bruising and purpura. If the symptoms are mild, usually there will be no need for treatment. Your child will need to have the full blood count repeated on a few occasions to check that the platelet numbers are stable and that the rest of the blood cell counts are remaining normal. If your child has bleeding and more severe bruising or purpura, treatment may be considered. The aim of treatment is to improve symptoms and increase the number of platelets.

If treatment is needed then the decision on what treatment to use can be difficult. This is because there have not been many studies done to test the treatments against each other. The options for treatment include:

• Prednisolone. This is often the first type of treatment tried. It is a steroid medication and is taken as syrup or tablets. This may be given as a high dose over a short period of time (four days) or as a lower dose for a longer time (two weeks). Prednisolone has been shown to increase the number of platelets quickly in about 3 in 4 children with ITP.
• Other steroid options. High dose methylprednisolone or high dose dexamethasone. These are other types of steroid drugs that have also been shown to be effective in differing degrees. However, dexamethasone is not often used in children.
• Intravenous immunoglobulin (IVIg). This is an injection of a protein into the bloodstream and has been shown to work well in about 8 in 10 children in increasing the number of platelets. It is not usually used as the first option because it involves an injection, can cause quite a lot of side effects, and is quite expensive. It may be used as an emergency treatment if your child has severe bleeding or needs surgery.
• Anti-D immunoglobulin. This is another type of protein that is also effective and causes less side effects than IVIg. It can only be given to children whose blood group is RhD positive.
• Platelet transfusions. In a life threatening situation your child may be given a transfusion of platelets at the same time as being treated with steroids and IVIg. This only helps to increase the number of platelets for a short time as the transfused platelets also get attacked by the antibody that the body has produced and are destroyed by the spleen.
• Other drugs. A number of other drugs are being trialled. These are not routinely recommended as not enough information is known yet about their use and side effects.
• Surgery to remove the spleen (splenectomy). This is very rarely done in children with ITP. It is only really considered as an option if your child has life threatening bleeding or severe chronic disease that is affecting their day to day functioning.

In chronic ITP, usually no treatment is needed but your child will need to have regular blood tests and specialist review. If they have an injury or are involved in an accident you will be advised to take them to your local hospital emergency department for review. If the disease is severe, then the treatments outlined above may be considered.

ITP IN ADULTS

How common is it?

In adults, ITP occurs in about 6 in 100,000 people. It is more common in women and predominantly occurs in women of child bearing age. It may also be seen more often in the elderly.

What are the symptoms?

In adults, ITP comes on gradually and it usually does not follow a viral illness. It is not really known what causes the disease. The symptoms may vary a lot. You may have no symptoms, purpura, mild bruising or bleeding, or severe bleeding. Unlike ITP in children, most adults with ITP will always have a low number of platelets. This is called chronic ITP.

How is it diagnosed?

Because most adults with ITP do not have any symptoms, ITP is usually diagnosed on a routine blood test that has been done for other reasons. The full blood count shows a lower number of platelets than normal. The laboratory will also look at your blood under a microscope.

Sometimes, usually in those over 60 or if your symptoms are unusual, a sample from your bone marrow (the inside of the bone) may be necessary. Low platelet numbers can be due to other causes such as medication, lupus, viral infections or other diseases. It may be necessary for you to have some additional tests to check for these.

What is the treatment?

Like children, most adults with ITP do not require active treatment unless they have significant symptoms or need to undergo surgery for any reason, including dental work. It is important to have adequate platelet levels before surgery in order to minimise the risk of severe bleeding during the procedure.

If treatment is needed, then the first treatments that tend to be used in an adult with ITP are usually steroids or IVIg. Both of these treatments increase the platelet count in about 2 or 3 people in 4. Usually though, this improvement is only temporary and the platelet numbers return to a low level after a few weeks.

Surgery to remove the spleen (splenectomy) is used more often in adults than children. It is more likely to result in a longer lasting normal number of platelets. About 2 in 3 people with ITP who have a splenectomy will have a normal long lasting number of platelets. However, splenectomy is not without possible complications. As the spleen is responsible for fighting certain types of infection, people who have had their spleen removed are more at risk of some serious infections. For this reason, you will need to have some extra vaccinations and may be advised to take antibiotics every day.

If the above measures do not work, then there are several other treatment options. For example, you may be given another trial of steroids or IVIg. Anti-D immunoglobulin can also be used in adults and has been shown to increase platelet numbers in up to 9 in 10 people. Other treatments that may be used include danazol and medications to suppress the immune system such as azathioprine or ciclosporin. There are many other treatments that are sometimes used if all other measures have not been successful. A number of new treatments and drugs are currently being trialled to see how well they work in ITP.

What if I am pregnant?

A low number of platelets in pregnancy is quite common. It can be difficult to know if your platelet count is low due to the pregnancy or due to ITP. If you have no symptoms and the number of platelets is not too low, then you may just be monitored. If the number of platelets needs to be increased, then steroids or IVIg can be used. A platelet count greater than 50 x 10⁹ per litre is generally considered safe for a normal vaginal delivery. A count greater than 80 x 10⁹ per litre is generally considered safe for a caesarean section. Your specialist will advise in your own particular situation.

It is very unlikely that your low number of platelets will cause any problems to your newborn baby. After they have been born, their platelet level will be checked and if it is low, they will be monitored carefully. If they need treatment, IVIg can be used.

What is the outlook (prognosis) of ITP in adults?

In adults, the outcome is very variable depending on the severity of symptoms. Most people do not need any treatment. If treatment is needed, the response to treatment varies from person to person.

Further information and support

ITP Support Association

Web: www.itpsupport.org.uk
Aims to promote and improve the general welfare of patients, and the families of patients, with Immune (Idiopathic) Thrombocytopenic Purpura.