Understanding Platelet Disorders

Platelets are small cell fragments in your blood that clump together and plug small breaks in blood vessels, the first step in stopping bleeding. A normal platelet count and normal platelet function are both necessary for this process to work properly. When either is disrupted, the result is a platelet disorder, which can cause too much bleeding, and in some cases, too much clotting.

Thrombocytopenia means a platelet count lower than normal, which increases the risk of bruising and bleeding. It can result from the bone marrow producing too few platelets, the body destroying platelets faster than they are made (as in immune thrombocytopenia, or ITP), or the spleen trapping and holding too many platelets.

Thrombocytosis means a platelet count higher than normal. It can be reactive, occurring temporarily in response to infection, inflammation, iron deficiency, or after surgery, or it can stem from a bone marrow condition that causes the marrow to overproduce platelets on its own.

Platelet function disorders involve a normal platelet count but platelets that do not work properly, meaning they do not clump and plug effectively even though there are enough of them. These can be inherited, such as some rare genetic conditions, or acquired, commonly from medications such as aspirin or other blood thinners.

Low platelet counts can be caused by viral infections, certain medications, autoimmune conditions where the immune system mistakenly attacks platelets, vitamin B12 or folate deficiency, liver disease, pregnancy-related changes, or bone marrow disorders including some blood cancers. High platelet counts are often reactive to another condition such as infection or iron deficiency, though a bone marrow-based cause is considered when the count is very high or persistent without another explanation.

Low platelet counts or poor platelet function can cause easy bruising, small red or purple spots on the skin called petechiae, prolonged bleeding from minor cuts, frequent nosebleeds or gum bleeding, heavier than usual menstrual bleeding, and in more severe cases, blood in urine or stool. High platelet counts often cause no symptoms at all and are usually found incidentally on a routine blood test, though very high counts can occasionally increase clotting risk.

A complete blood count is the starting point, showing whether the platelet count itself is abnormal. A peripheral blood smear lets a doctor examine platelet size and appearance under a microscope, which can offer clues to the underlying cause. Depending on findings, further tests may include markers for autoimmune conditions, vitamin levels, liver function tests, or a bone marrow biopsy if a marrow-based cause is suspected.

Treatment is directed at the underlying cause rather than the platelet count alone. Mild, incidental low counts with no bleeding symptoms may simply be monitored. Immune thrombocytopenia may be treated with medications that reduce the immune attack on platelets, such as corticosteroids, when the count is low enough to pose a bleeding risk. Reactive high platelet counts typically resolve once the underlying trigger, such as an infection or iron deficiency, is treated. Platelet counts that are dangerously low, or bleeding that is active, may require a platelet transfusion. A clinical haematologist tailors the approach based on the cause, the platelet count, and whether symptoms are present.