Understanding thrombocytopenia: a consultant haematologist's guide
Thrombocytopenia is a medical term that refers to a low platelet count in the blood. Platelets, also known as thrombocytes, are small cell fragments that play a vital role in helping the blood to clot, and without them, many complications can occur. In this article, consultant haematologist Dr Drew Provan explains how thrombocytopenia occurs, the risks of the condition, and how it can be managed.
In the blood normal platelet count ranges from 150 to 400 x 10⁹/L. When the number drops below this, it increases the risk of bruising, bleeding, and other complications, depending on the severity.
Thrombocytopenia can vary in seriousness. For some patients, they have no symptoms and it is incidentally diagnosed during a blood test (as part of a checkup or when investigating a different health concern). For others, especially when platelet counts are significantly reduced, it can lead to dangerous and uncontrolled bleeding episodes, requiring urgent medical attention.
What causes thrombocytopenia?
Thrombocytopenia can affect people of any age, from children to older adults. It can arise from a wide range of causes, which are generally grouped into three categories: reduced platelet production, increased platelet destruction, or platelet sequestration (where platelets are trapped in an enlarged spleen).
One well-known immune-related cause is immune thrombocytopenia (ITP). This is an autoimmune disorder in which the body’s immune system mistakenly attacks and destroys its own platelets. ITP can occur in both children and adults and may follow a viral infection. In many children, it resolves on its own, but in adults it is more likely to become a chronic condition.
Other causes of thrombocytopenia include certain medications (such as chemotherapy or antibiotics), viral infections like HIV or hepatitis C, bone marrow disorders (such as leukaemia or aplastic anaemia), liver disease, and excessive alcohol consumption.
Pregnancy can also lead to a mild form of thrombocytopenia in some women, usually in the third trimester. This is known as gestational thrombocytopenia and is typically harmless, though it does need monitoring.
Symptoms of thrombocytopenia
Many people with a mild reduction in platelets will experience no symptoms at all. However, as platelet levels drop, symptoms may begin to appear. These can include:
- Easy or excessive bruising
- Small red or purple spots on the skin (known as petechiae)
- Bleeding gums or nosebleeds
- Prolonged bleeding from cuts
- Blood in urine or stools
- In women, heavier than normal periods
When platelet levels fall to very low levels (typically below 30 x 10⁹/L), there is a higher risk of serious internal bleeding, including in the gastrointestinal tract or, rarely, the brain. This is considered a medical emergency.
Diagnosing thrombocytopenia
The diagnosis of thrombocytopenia begins with a full blood count (FBC), a routine blood test that measures all the different cells in the blood. If the platelet count is low, further investigations are required to determine the underlying cause.
These may include a blood analysis to look at the shape and appearance of blood cells under the microscope, liver function tests, viral screening, and autoimmune tests. In some cases, a bone marrow biopsy may be necessary to assess platelet production directly within the marrow.
An accurate diagnosis is essential to guide the appropriate treatment, as the management will differ depending on the cause.
Treatment options for thrombocytopenia
Treatment depends on both the cause and severity of the thrombocytopenia. If the platelet count is only mildly reduced and the patient has no symptoms, regular monitoring may be all that is needed.
In cases of immune thrombocytopenia, treatment is often needed when the platelet count is dangerously low or if bleeding is occurring. first-line therapies include steroids, which help suppress the immune system, and intravenous immunoglobulin (IVIG) to temporarily increase platelet levels. If these are not effective, other options such as rituximab, thrombopoietin receptor agonists, or even splenectomy (removal of the spleen) may be considered.
For thrombocytopenia caused by other conditions, such as medications, infections, or liver disease, the primary approach is to treat the underlying cause. Platelet transfusions may be used in emergencies or during surgery when platelet counts are dangerously low.