What is ITP
Immune thrombocytopenia (formerly known as idiopathic thrombocytopenic purpura) is a medical term for an autoimmune disorder (immune) causing a shortage of platelets (thrombocytopenia) and bruising (purpura).
What is the cause of ITP
ITP is an autoimmune disease in which the immune system mistakes the platelets as being foreign and destroys them. It can follow a virus, vaccination or certain medications, but for most people the cause is unknown.
ITP that arises suddenly is known as acute ITP, if the platelet count remains low after 3 months it will be called persistent ITP, and if the platelet count has not returned to normal after 6 months it will be called chronic ITP. The severity of the condition is determined by adding the names severe or mild. Thus, for example, someone with chronic severe ITP would have had a troublesome condition with a very low platelet count for more than 6 months.
How is ITP diagnosed?
ITP is usually diagnosed by a blood test showing that only the platelet count is low, and the platelets, red blood cells and white blood cells all look normal. A bone marrow biopsy may be taken at a later stage if the ITP continues, in which a small sample of bone marrow will be taken under local anaesthetic and examined under the microscope. Additional blood tests may be taken at this time to exclude rare clotting or immune diseases that can mimic ITP. If the bone marrow looks normal, with the usual or higher number of platelet parent cells (megakaryocytes) and other blood tests are normal then the doctor will diagnose chronic ITP.
What are platelets?
There are three types of blood cell which are all formed in the bone marrow; red cells, white cells and platelets. Platelets, which are small and sticky and circulate in the bloodstream provide the inital plug to stop bruising and bleeding after an injury, and stop blood leaking from capilleries. A blood sample is taken to measure the circulating platelets, and in most people there are between 150,000 and 400,000 platelets in every cubic millimetre of blood. However in the UK we simplify this by describing a platelet count of, say, 150 rather than 150,000. Anyone with a count less than 100 would be considered thrombocytopenic (ie. short of platelets). Many people with ITP have a platelet count in single figures, and on rare occasions there are not enough circulating platelets to be counted, thus the count is given as 0. The number of platelets circulating in our bodies fluctuates all the time, and thus no two consecutive platelet counts are likely to be exactly the same either in a healthy person or in an ITP sufferer.
What is the difference between ITP and hæmophilia?
Hæmophilia is inherited and permanent, ITP is not inherited, and can go into remission. Hæmophilia patients are deficient in one of the 12 factors which act together to form a blood clot. ITP patients are short of platelets which work independently as the initial plug to stop blood leakage, but the rest of the clotting mechanism works normally. Platelet infusions are only used in emergencies as transfused platelets, like the patient’s own platelets, are destroyed by their immune system in a matter of hours.
What is the incidence of ITP?
In the UK about 3,000 to 4,000 of the population have ITP at any one time, and it is not more prevalent in any particular racial or ethnic group.
What are the symptoms of ITP?
Some people with ITP, especially those with a count over 50, may have no symptoms at all, and their ITP only noticed during a routine blood test. Even people with very low counts, can sometimes have few symptoms.
Common symptoms are:
petechiae (pinprick rash of blood spots)
black mouth blisters
Rare symptoms are:
blood in the eyes
bleeding from the ears
blood in the urine
bleeding from the gut
bleed into the brain
How is ITP treated?
Some adults with mild ITP may not need any treatment, but will be monitored with occasional blood tests. There is no cure for ITP and treatment is used to raise the platelet count to counteract symptoms.
First line treatments include prednisolone and intravenous immunoglobulin (under various brand names).
Second line treatments include splenectomy, azathioprine, cyclosporin, cyclophosphamide, vinca alkaloids, danazol, dapsone, rituximab, eltrombopag, romiplostim and mycophenlate mofetil.
Tranexamic acid may be used for dental extractions. Hormone preparations and/or tranexamic acid may be prescribed to women having heavy periods.
Platelet transfusions may be used to stem active bleeding or during surgery, but they are ineffective as a treatment for ITP as the immune system destroys transfused platelets as quickly as the body’s own platelets.
When to seek help?
You should contact the hospital in the following circumstances:
A prolonged (over 30 minutes) nosebleed which will not stop despite pinching the nose
Prolonged gum bleeding
Blood in the faeces or urine
A heavy blow to the head
Persistent or severe headache with loss of vision, vomiting or drowsiness
Very heavy periods (eg. lasting 8 -10 days, changing more than 9 tampons/pads per day, changing protection during the night, passing clots on 2 consecutive days)
The ITP Support Association is grateful to Professor Adrian Newland and Dr John Grainger for their assistance in the preparation of this page.
Further reading: The ITP Support Association's core booklet Know About ITP (free to members and sent out with the initial information pack) explains about ITP, its management, treatment options, general outlook, ITP in pregnancy, and referral and second opinion on the NHS.