Thrombocytopenia (Low Platelet Count)

What platelets do

Platelets are small cell fragments made in the bone marrow that circulate for about 7 to 10 days. When a blood vessel is injured, they stick to the damaged area and to each other to form a plug, and help the clotting process. About a third of platelets are normally stored in the spleen.

Causes of thrombocytopenia

Low platelets happen through four main mechanisms:

Reduced production in the bone marrow

• Leukemia, lymphoma and myelodysplastic syndrome
• Aplastic anemia
• Chemotherapy and radiation
• Vitamin B12 and folate deficiency
• Heavy alcohol use
• Viral infections (HIV, hepatitis C, Epstein-Barr, measles)
• Inherited conditions (such as Wiskott-Aldrich syndrome)

Increased destruction

• Immune thrombocytopenia (ITP): the immune system destroys platelets. In children it often follows a viral infection and resolves within months. In adults it is more often chronic
• Drug-induced: heparin (HIT, which paradoxically causes clots), quinine, some antibiotics, anticonvulsants and others
• Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS): platelets consumed in small clots, with anemia and organ damage. These are emergencies
• Disseminated intravascular coagulation in severe illness
• Autoimmune diseases such as lupus
• Infections including sepsis and dengue

Sequestration in an enlarged spleen

Liver disease and cirrhosis with portal hypertension cause the spleen to enlarge and trap platelets.

Dilution and pregnancy

• Large blood transfusions
• Gestational thrombocytopenia: a mild, harmless fall in late pregnancy affecting about 5 to 10% of pregnancies. Severe pregnancy-related causes such as HELLP syndrome must be excluded

Pseudothrombocytopenia

A falsely low count when platelets clump in the test tube. Repeating the test in a different tube (citrate) gives the true count.

Symptoms

• Easy bruising
• Petechiae: pinpoint red or purple spots, often on the lower legs
• Purpura: larger purple patches
• Nosebleeds and bleeding gums
• Prolonged bleeding from cuts
• Heavy menstrual periods
• Blood in urine or stool
• Fatigue and other symptoms of the underlying cause

Platelet levels and bleeding risk

Bleeding risk also depends on the cause, platelet function, age, and other medicines.

Diagnosis

1. Repeat complete blood count and blood smear to confirm the count, look at platelet size and clumping, and check other blood cells.
2. History: medicines (including heparin, supplements and quinine in tonic water), alcohol, infections, pregnancy, family history.
3. Tests depending on the cause: liver function, kidney function, HIV and hepatitis C, B12 and folate, clotting tests, ADAMTS13 for TTP, heparin antibodies for HIT.
4. Ultrasound of the abdomen for an enlarged spleen or liver disease.
5. Bone marrow biopsy if marrow disease is suspected.

Treatment

• Mild cases without bleeding often need only monitoring and treatment of the cause.
• Stop suspected medicines. In HIT, heparin is stopped and a non-heparin blood thinner is started.
• ITP: treatment is usually given if the count is very low or there is bleeding. Options include corticosteroids, IV immunoglobulin, thrombopoietin receptor agonists (eltrombopag, romiplostim, avatrombopag), rituximab, fostamatinib and, rarely, spleen removal.
• TTP: urgent plasma exchange, steroids and caplacizumab.
• Platelet transfusion for active bleeding, before procedures, or for very low counts from marrow failure. It is usually avoided in TTP and HIT unless bleeding is life-threatening.
• Treat the underlying condition, such as infection, liver disease or vitamin deficiency.

Living with low platelets

• Avoid aspirin, NSAIDs and supplements that affect clotting unless your doctor approves
• Use a soft toothbrush and electric razor
• Avoid contact sports when the count is low
• Limit alcohol
• Tell all healthcare providers and dentists about your platelet count

Frequently asked questions

What causes low platelets?

Low platelets can result from reduced production (bone marrow disorders, chemotherapy, vitamin deficiencies, alcohol, viral infections), increased destruction (immune thrombocytopenia, medicines, TTP), trapping in an enlarged spleen from liver disease, or mild drops in pregnancy.

What is a dangerously low platelet count?

Counts below about 10,000 to 20,000 per microliter carry a risk of spontaneous serious bleeding. Below 50,000, bleeding after injury or surgery is more likely. The risk depends on the cause and other factors, so any count below 50,000 needs medical advice.

What are the symptoms of thrombocytopenia?

Many people have no symptoms. When present, symptoms include easy bruising, tiny red or purple skin spots, nosebleeds, bleeding gums, heavy periods, prolonged bleeding from cuts, and blood in urine or stool.

Can low platelets be cured?

It depends on the cause. Drug-induced and infection-related thrombocytopenia often resolve once the trigger is removed. Childhood ITP usually goes away within months. Chronic ITP and marrow disorders may need long-term treatment.

Is thrombocytopenia in pregnancy dangerous?

Gestational thrombocytopenia, a mild drop in late pregnancy, is common and harmless. However, low platelets can also signal preeclampsia, HELLP syndrome or ITP, so they are monitored closely during pregnancy.