Platelets are tiny components of the blood which help blood to clot when we injure ourselves. They are also known as thrombocytes. They are made inside bone, in the bone marrow. They are released into 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 ribs on the left-hand side.
A normal number of platelets is between 150 and 400 x 109 per litre. This is found by a blood test. 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 than usual.
What is idiopathic thrombocytopenic purpura?
Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease involving platelets. In autoimmune disorders your body makes an antibody that damages another part of your body. In ITP the antibodies are made against platelets. Once the antibodies have attached to platelets, the platelets do not work so well. They are also removed more quickly by the spleen because they are abnormal.
- Idiopathic means that there is no known underlying cause found.
- Thrombocytopenic means not enough platelets.
- Purpura is a purple-red rash.
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.
IDIOPATHIC THROMBOCYTOPENIC PURPURA IN CHILDREN
How common is it in children?
ITP occurs in about 5 in 100,000 children. Girls are three times more likely to have it than boys.
What are the symptoms?
- Most children will not have any symptoms.
- Those who do develop symptoms have bruising and the rash – purpura. Some have bleeding such as nosebleeds. It usually appears over 1-2 days. The condition often occurs about 2-3 weeks after an infection (often a common viral infection). Occasionally, it follows immunisation. The symptoms disappear over 6-8 weeks in most cases.
- Very occasionally, it causes severe bleeding which requires emergency treatment.
- The platelet levels in about 1 in 10 affected children do 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 few cases, the immune system continues to be faulty and the condition becomes long-standing.
How is it diagnosed?
ITP is diagnosed by a blood test called a full blood count. This test shows that there are fewer platelets than normal. The laboratory will also have a look at the blood under a microscope.
Sometimes different tests will be needed to make sure that the low number of platelets is not due to another of the potential causes. Rarely, this involves taking a sample of bone marrow.
What is the treatment?
Most children will not need 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 testing 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 medicines that have also been shown to be effective in differing degrees. 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. It can also 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 fewer 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. The transfused platelets are also attacked by the antibody that the body has produced and are destroyed by the spleen.
- Other medicines. A number of other medicines 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.
IDIOPATHIC THROMBOCYTOPENIC PURPURA IN ADULTS
How common is it?
ITP occurs in about 6 in 100,000 adults. It is more common in women, and particularly 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 does not usually 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 continue to have a low number of platelets indefinitely. 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 aged over 60, or if your symptoms are unusual) a sample from your bone marrow 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 rule out these other conditions.
What is the treatment?
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 operation.
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 in 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. See separate leaflet called ‘Splenectomy – Ongoing Prevention of Infection’ for further details.
If the above treatments do not work, there are several other 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. A medicine called rituximab has also produced good responses in around 6 in 10 treated people. Other new treatments are currently being researched, 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, 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?
In adults, the outcome is 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.
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