Thrombocytopenia is a shortage of platelets. If you don’t have a normal number of platelets, doctors say that you are ‘thrombocytopenic’.
Platelets are made in the bone marrow (the spongy centre of some bones). They develop from huge cells in the bone marrow called ‘megakaryocytes’. Usually platelets stay in the bloodstream for about 10 days before they are removed by the spleen. The bone marrow works all the time to make new platelets. It works harder if platelets are needed to stop bleeding somewhere in your body.
The number of platelets in your blood is measured by a test called the full blood count (FBC). Doctors talk about a ‘range’ of normal results because some people naturally have higher or lower levels than others. Different hospitals use slightly different ranges. Your doctor should tell you what is considered normal at your hospital. They are likely to say something like ‘more than 150 is normal’. The ‘150’ means 150 million platelets per millilitre (mL) of blood. This is a bit of a mouthful so doctors and nurses talk about platelets being 150 (or 50 or 20, for example, if they are low).
Platelets are needed for the first stage of blood clotting. When you cut yourself or damage a blood vessel, the platelets fill up the hole, forming a platelet plug. The second stage involves clotting factors (proteins in the blood), which then bind everything together while the area heals.
If you have a low number of platelets, it is harder for you to form a blood clot. This means you may bleed for longer if you cut yourself. You may also bruise more easily than normal.
Possible causes of low platelets when you have lymphoma are:
- lymphoma in the bone marrow
- a side effect of treatments for lymphoma including chemotherapy and some of the newer, targeted therapies
- platelets being used up or removed from the blood too fast for the bone marrow to keep up, which may be caused by
Lymphoma in the bone marrow
If lymphoma cells are in the bone marrow, they take up space that is normally used to produce healthy blood cells. This can lower the number of platelets your bone marrow makes, meaning you have fewer platelets and become thrombocytopenic.
This type of thrombocytopenia often begins to improve once treatment for the lymphoma has started to work.
A side effect of treatment
Although the aim of chemotherapy is to kill the lymphoma cells, a side effect of many types of chemotherapy is the destruction of some healthy cells. This can affect the megakaryocytes in the bone marrow that would normally make new platelets. If the number of new platelets made doesn’t meet the number needed in the bloodstream, the platelet count falls.
If it is going to occur, thrombocytopenia usually starts about 6–10 days after the start of chemotherapy. Not all treatments result in thrombocytopenia. How low your platelet levels go after treatment and for how long depends on:
- how strong your chemotherapy is
- whether you had lymphoma in the bone marrow before you started treatment.
Some of the newer targeted therapies can cause thrombocytopenia and increase the risk of bleeding. Ibrutinib (Imbruvica®) may cause bleeding because of its effect on the way platelets work, without affecting their number. Because of this, it isn’t usually given to people who are taking drugs to thin the blood, such as warfarin. Bortezomib (Velcade®), obinutuzumab (Gazyvaro®) and lenalidomide (Revlimid®) can also cause low platelet levels.
Radiotherapy doesn’t normally have much of an effect on the bone marrow. It doesn’t usually cause low platelet levels on its own.
As well as being found in the blood, some of the body’s platelets are always found in the spleen. If the spleen is bigger than normal (splenomegaly), there is space in it for more platelets. As a result, the platelets tend to collect in the spleen, leaving fewer than normal in the bloodstream.
Treatments that shrink the spleen may help if this is the cause of your thrombocytopenia. Sometimes the spleen is removed (splenectomy). This may be done to treat the lymphoma but usually helps improve platelet levels too.
Sometimes the body’s immune system starts to make antibodies against cells within the body. These antibodies are known as ‘autoantibodies’.
If the autoantibodies stick to platelets, these platelets are removed when they pass through the spleen. When the bone marrow can’t make new platelets fast enough to replace the ones lost, thrombocytopenia develops. This type of thrombocytopenia is known as ‘immune thrombocytopenic purpura' (ITP). It happens more often in people with low-grade lymphomas, such as chronic lymphocytic leukaemia (CLL).
In addition to thrombocytopenia, people with lymphoma may be more likely to bleed for other reasons. These include:
- having another problem with blood clotting, for example, lymphoma in the liver might mean fewer clotting factors are made
- being on other drugs that affect blood clotting, such as aspirin, heparin or warfarin
- having a fever (high temperature) as this tends to use up platelets faster and make bleeding worse.
Having low platelets does not make you feel any different. Most people who have a platelet count that is below the normal range have no symptoms at all. This is because the body has a built-in reserve with many more platelets than are needed for day-to-day life.
If your platelet count falls to very low levels, symptoms become more likely. A general guide to what you might expect with different numbers of platelets is:
- slightly low platelets (above 50) – probably no symptoms at all
- low platelets (20–50) – you may bruise more easily and bleed for longer if you cut yourself
- very low platelets (10–20) – you will probably bruise more easily, bleed for longer if you cut yourself and may start to notice bleeding even without an obvious cause
- extremely low platelets (below 10) – you are at risk of bleeding, even without an obvious cause.
The bleeding you may notice if your platelets are very low includes:
- mouth or gum bleeding
- heavy periods in women
- blood in urine
- bleeding from the bowel – this can be obvious blood or may make your stools black in colour.
As well as bruising more easily, you may also notice purpura (petechia). These are small red or purple spots on the skin (often on the legs) or on the lips or in the mouth. They can appear temporarily when platelets are very low.
If bleeding goes unnoticed, it can also cause anaemia.
What should you do if you start bleeding?
The key to avoiding serious problems caused by low platelets is to get in touch with your hospital quickly if you start bleeding.
Let your medical team know if you develop any of the mentioned symptoms. If you are bruising easily or are feeling tired, your doctor may arrange a blood test. If you are bleeding, they may want to see you more quickly in the hospital. Remember, if your platelets are very low and you are bleeding, the situation will only get worse. It is always better to be checked over and have treatment early if needed.
Many people who have times when their platelets are low because of chemotherapy need no treatment at all. Their bone marrow stops working only briefly and their platelets quickly return to a safe level. As a result, they have a higher risk of bleeding for a very short time only.
For those who experience bleeding, treatments can include:
Platelet transfusions don’t work well for immune thrombocytopenic purpura (ITP). Instead, treatment for ITP aims to lower the levels of the autoantibody.
There are drugs that boost the megakaryocytes to make more platelets (thrombopoietin receptor agonists). These are similar to the growth factors G-CSF (used to raise the white blood cell count) and erythropoietin (used to treat anaemia). They are sometimes used to treat ITP. At present, they are not used to treat thrombocytopenia that is caused by chemotherapy.
Changes to other drugs
If you are on warfarin, heparin or aspirin and develop bleeding, you might need to stop taking the blood thinner or lower its dose. This might also be done if your platelets are low, especially if you have liver problems too. Your medical team will tell you if you need to make changes; always check with them before you stop, start, or change the dose of your drugs.
Occasionally, other treatments to help your blood clot, such as vitamin K or an infusion of fresh frozen plasma (FFP), might be needed.
If you are bleeding and your platelets are low, you may be given a platelet transfusion. This is similar to a blood transfusion given for anaemia, except it takes only about half an hour. Platelet transfusions are as safe as other blood transfusions.
The platelets that are given do not make the platelet count normal again. Instead, they stop any bleeding that’s already occurred or lower the risk of further loss of blood. Because the platelets get used up, the effect only lasts for a few days.
Platelet transfusions are usually given only to:
- people who are actively bleeding and have a low platelet count
- people who have an extremely low platelet count, which makes them likely to bleed
- people who have a low platelet count and need to have an operation or another significant medical procedure.
Treatments for immune thrombocytopenia
If your thrombocytopenia is caused by autoantibodies destroying your platelets, platelet transfusions will not help. Instead, the treatment of this type of thrombocytopenia aims to reduce how much autoantibody is being made. This is usually done, at least at first, by giving you steroids, often prednisolone. The dose of steroid is high to begin with and this may cause irritation to your stomach. You may be given another drug to protect your stomach.
Once your platelets are no longer being destroyed, the dose of steroid is lowered.
Treating your lymphoma may also help to stop the autoantibodies being made. Rituximab (MabThera®), with or without chemotherapy, tends to reduce the number of autoantibodies as well as kill the lymphoma cells.
You cannot stop yourself becoming thrombocytopenic, but the following advice may make you less likely to bleed if you have low platelets (your medical team should tell you what is sensible for you):
- avoid high-impact sports (eg long-distance running) and contact sports (eg rugby)
- wear gloves, long sleeves and long trousers to help protect you from scratches and cuts when gardening or doing DIY
- take extra care to avoid cutting yourself when using knives to prepare food
- avoid blowing your nose too hard or too often
- use an electric razor over wet shaving
- brush your teeth regularly but gently using a soft-bristled toothbrush (eg a child’s toothbrush)
- avoid flossing your teeth if it causes bleeding.