Health Centres - Idiopathic thrombocytopenic purpura (ITP)
What is ITP?
Thrombocytopenia is the medical term for a low platelet count. Idiopathic means unknown cause. Purpura refers to the pin-prick bleeding under the surface of the skin that is a symptom of the low platelet count.
In ITP, antibodies coat the surfaces of the platelets, destroying them and causing their level to drop.
For a full description of platelets and the causes and effects of a low platelet count, see the factsheet on thrombocytopenia.
Types of ITP
ITP can be divided into two different forms.
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Acute ITP starts suddenly and usually follows a viral illness in a child. Acute ITP may require no treatment, especially if the platelet count does not fall too low and there is little bleeding. It usually improves spontaneously and, in children at least, rarely comes back.
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Chronic ITP develops over time, is long lasting and more common in adults. It may not need treatment if the platelet level doesn't pose a significant risk of bleeding. Any such assessment should take account of your lifestyle, such as participation in contact sports or manual work.
The features of childhood and adult ITP are compared in the table below.
| ITP in children and adults | Child | Adult |
| Age most likely to occur (years) | 2-6 | 20-30 |
| Gender ratio of disease (M:F) | 1:1 | 1:3 |
| Start of disease | acute | subtle |
| Preceding infection | common | unusual |
| Platelet count (x 10 |
often <20 | often >20 |
| Spontaneous remission rate (% | >80 | <20 |
| Usual duration | 2-4 weeks | months-years |
The initial treatment for acute and chronic ITP is similar. A variety of agents are used, including oral steroids, infusions of immunoglobulin or more rarely anti-D.
Side-effects include:
- influences on mood (elation, depression, vivid dreams)
Prolonged use of steroids is also associated with osteoporosis.
Acute ITP often responds to a three to four week course of steroids, after which treatment is stopped.
In chronic ITP there may be an initial improvement, but the platelet count falls again once the dose is reduced or withdrawn. If this happens, you may need an alternative treatment or a long-term low dose steroid plus measures to protect against osteoporosis, for example medicines and monitoring of bone density.
Immunoglobulin
If the foreign protein appears again in the body at a later date, it is 'recognised' by the antibody which then activates the rest of the immune system.
It can take the body days or weeks to make immunoglobulins in response to a foreign protein, but they can be pooled from donated human blood and given by injection.
The type of immunoglobulin used for ITP is called immunoglobulin G (IgG). It's given intravenously, usually over two to five days.
The precise action of IgG in ITP is unknown, but it's thought to block platelet removal and so increase their number. IgG treatment provides only a temporary response, so it is mainly of benefit in acute ITP.
In chronic ITP it may be used when a temporary rise in platelets is desired or during pregnancy because the risk to the baby is less than with other treatments.
Anti-D antibody
Alternative treatments for ITP
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other forms of immune suppression with drugs such as cyclophosphamide, azathioprine, vincristine, danazol, cyclosporine A and mycophenolate
It usually takes two to three months before azathioprine and cyclophosphamide have any effect on the platelet count. During this time they should be carefully monitored, because they have other toxic effects such as disturbed liver function, bone marrow suppression and effects upon fertility.
Mycophenolate can also be slow acting in ITP. Again, you should be monitored for side-effects such as abnormal blood count (usually low white cell count) or abnormal liver function tests. In some people this drug causes problems in the stomach and intestine.
Danazol is a synthetic androgen (male hormone-like drug). It is successful for about half of those patients who do not respond to other treatment, but has to be used with caution. Its side-effects include abnormal liver function, acne, weight gain and increased body hair.
Cyclosporin A is a drug that suppresses certain aspects of the immune system. It is often used in patients who have had a transplant to prevent rejection of the organ. Some people with chronic ITP achieve a response to this drug.
You will need monitoring on this medicine: it can increase blood pressure and worsen kidney function. Some patients who are on cyclosporine for a long time develop enlarged gums.
Removal of the spleen (splenectomy)
In chronic ITP, surgery to remove the spleen is an option if the platelet count remains too low or doesn't respond to treatment. Only about 10 per cent of children with acute ITP have the operation.
Removing the spleen is a major operation and usually requires 7 to 10 days in hospital, although some surgeons are now able to remove the spleen using keyhole surgery. About two thirds of patients respond to splenectomy, but some of these eventually relapse.
Splenectomy is not generally considered in the early phases of ITP, in pregnancy or in children under six.
Haemophilus influenza type B, which can cause serious infection of the airways.
Meningococcal vaccine, against the organism which causes bacterial meningitis.
- increased appetite
- weight gain
- facial puffiness
- high blood sugar
- worsening of high blood pressure
- indigestion
- suppressed immune response resulting in an increased risk of infections, especially chickenpox.
Immunoglobulins are antibodies that are made by the immune system following exposure to a foreign protein, for example a virus.
An alternative approach is to use anti-D, which contains antibodies to the rhesus blood group protein 'D'. This works in a similar way to IgG, but is administered as a single injection that can be repeated. Many centres now give anti-D instead of IgG, because it is equally effective and simpler to give.
These include:
- repeated short doses of a steroid known as dexamethasone.
The spleen sits under the rib cage on the left side of the abdomen. One of its functions is to remove old red blood cells. In most patients with ITP, it is the main site of platelet destruction.
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