Immune thrombocytopenia (ITP): symptoms, platelet counts and treatment

Platelets are small, sticky cells made in the bone marrow that form the first plug to stop bleeding after an injury. In ITP, as Hull University Teaching Hospitals explains, the immune system mistakes platelets for a threat and makes antibodies that destroy them. Cambridge University Hospitals adds that this happens mainly in the spleen.

In most people the cause is unknown. The Hull leaflet says ITP can follow a virus, vaccination or certain medicines. Cambridge describes primary ITP, where the reason for the autoantibody is unknown, and secondary ITP, where another condition predisposes to it, such as other autoimmune conditions like rheumatoid arthritis, or infections such as hepatitis or HIV.

ITP is different from haemophilia. Hull points out that haemophilia is inherited and permanent, whereas ITP is not inherited and can go into remission, and that in ITP the rest of the clotting system works normally.

Bleeding is the most common symptom of a low platelet count, but the Hull leaflet says it usually happens only when platelets drop to a very low number. Fatigue is also common, particularly when counts are very low, and if bleeding causes iron levels to fall it can worsen tiredness, though it usually improves when ITP gets better.

• Pinprick rash of tiny blood spots under the skin (petechiae).

• Easy bruising.

• Nosebleeds and bleeding gums.

• Black or blood-filled blisters in the mouth.

• Heavy periods.

• Rarely: blood in the eyes, bleeding from the ears, blood in the urine or other serious bleeding.

The Hull leaflet says ITP is usually diagnosed from a blood test showing that only the platelet count is low, while red cells, white cells and the platelets themselves look normal under a microscope. Further blood tests may exclude rare clotting or immune conditions that mimic ITP, and a bone marrow biopsy may be done later if ITP continues, though it is not needed for most people.

Cambridge says no test is completely accurate for diagnosing ITP, and when someone does not respond to steroids the doctors will look for another reason for the low platelets, which may mean extra blood tests including checks for infection, or a bone marrow test.

The Hull leaflet describes stages by duration: acute ITP when it occurs suddenly, persistent ITP if the count stays low after 3 months and chronic ITP if the count has not returned to normal after 12 months, with mild or severe added to describe how low the count is. It says about 3,000 to 4,000 people in the UK have ITP at any one time.

ITP does not always need treatment, even when platelet counts are low. Hull says in most cases doctors simply monitor, with treatment used for situations such as severe bleeding or before surgery. Cambridge says the goal is to reduce or stop bleeding rather than to hit a specific platelet target, and that an operation is considered safe as long as the platelet count is more than 50.

Cambridge also notes that many people with ITP have a platelet count below normal but come to no harm and need no treatment, which it calls being in remission. It says doctors will not usually recommend treatment unless there are bleeding symptoms or the count is very low, usually below 20, because all treatments have possible side effects.

Steroids are usually the first treatment. Cambridge says they work by stopping the immune system destroying platelets and are usually given as a short course, less than six weeks, while Hull says the dose is gradually reduced before stopping. Steroids should never be stopped suddenly without medical advice, and anyone on a longer course is given a steroid treatment card.

Cambridge says that for every ten adults treated with steroids, only three at most will not need further treatment. In the other seven the count drops again and more treatment may be needed. Reasons to try alternatives include not responding, relapsing when the dose is cut or not wanting repeated courses because of side effects.

The Hull leaflet advises contacting the hospital for a nosebleed lasting more than 30 minutes despite pinching, prolonged gum bleeding, blood in the faeces or urine, a heavy blow to the head, a persistent or severe headache with loss of vision, vomiting or drowsiness, very heavy periods, a sudden increase in bruising, and before any planned procedure. Anyone attending hospital for any reason should say that they have ITP.

Some ITP treatments reduce the ability to fight infection. Cambridge advises telling the clinical team about an unexplained high temperature, sore throat, mouth ulcers or other signs of infection. A head injury, uncontrolled bleeding or severe headache with vomiting or drowsiness is an emergency requiring 999 or A&E.