What are the causes of thrombocytopenia? A comprehensive guide

October 2, 2025 •

3 min read

Thrombocytopenia, a condition where the blood has an abnormally low number of platelets, affects a significant number of people and can range from mild and asymptomatic to severe and life-threatening. Understanding what are the causes of thrombocytopenia is the first step toward effective diagnosis and management.

Quick Summary

Thrombocytopenia can result from three primary issues: a failure of the bone marrow to produce enough platelets, the accelerated destruction or consumption of platelets in the bloodstream, or the sequestration of platelets within an enlarged spleen.

Key Points

Platelet Production Issues: Conditions like leukemia, aplastic anemia, or chemotherapy can suppress bone marrow function, leading to decreased platelet production.
Platelet Destruction: Autoimmune disorders (ITP, lupus), infections (sepsis, HIV), and certain drugs (heparin, some antibiotics) can cause platelets to be destroyed faster than they are made.
Splenic Sequestration: An enlarged spleen, often due to liver disease or cancer, can trap platelets, removing them from circulation and lowering the overall count.
Drug-Induced Thrombocytopenia: Medications, including common blood thinners and some antibiotics, can trigger an immune reaction leading to platelet destruction.
Infections as a Trigger: Both viral (HIV, hepatitis C) and bacterial (sepsis) infections can cause or exacerbate thrombocytopenia through immune responses or bone marrow suppression.
Pregnancy-Related Causes: Mild gestational thrombocytopenia is common, but more serious conditions like preeclampsia or HELLP syndrome can also cause low platelet counts during pregnancy.

Understanding Thrombocytopenia

Thrombocytopenia is defined as a platelet count below 150,000 per microliter of blood. Platelets, or thrombocytes, are tiny, disc-shaped cell fragments produced in the bone marrow that are essential for blood clotting. When their numbers drop, a person is at risk for excessive bleeding and bruising. The severity of the condition and the associated risks are directly linked to the underlying cause.

The Three Main Categories of Thrombocytopenia Causes

The myriad of conditions that can lead to a low platelet count are typically grouped into three broad categories based on the primary mechanism of action:

Decreased Production: The bone marrow, where platelets are made, fails to produce an adequate number of platelets.
Increased Destruction: The body's platelets are used up or destroyed at a rate faster than the bone marrow can replace them.
Sequestration: The spleen traps an excessive number of platelets, removing them from circulation.

Decreased Platelet Production

This occurs when the bone marrow's ability to create platelets is compromised. This can be due to bone marrow disorders like leukemia, lymphoma, aplastic anemia, or myelodysplastic syndrome. Chemotherapy and radiation can also damage bone marrow stem cells. Viral infections such as HIV, hepatitis C, and parvovirus, nutrient deficiencies (vitamin B12 or folate), heavy alcohol use, and some rare inherited conditions can also suppress bone marrow activity.

Increased Platelet Destruction or Consumption

In these cases, platelets are eliminated too quickly despite normal bone marrow function. This includes autoimmune diseases like immune thrombocytopenia (ITP), lupus, and rheumatoid arthritis, where the immune system attacks platelets. Certain medications, such as heparin, antibiotics, and anti-seizure drugs, can also trigger immune-mediated destruction (drug-induced thrombocytopenia). Severe infections (sepsis) can lead to disseminated intravascular coagulation (DIC), consuming platelets. Other causes in this category include thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), gestational thrombocytopenia during pregnancy, and, rarely, reactions to blood transfusions.

Splenic Sequestration

An enlarged spleen (splenomegaly) can trap an excessive number of platelets, reducing their circulation. Normally, the spleen holds about one-third of platelets. Conditions causing splenomegaly, such as liver disease (cirrhosis), certain cancers, and severe infections, can lead to thrombocytopenia through this mechanism.

A Comparison of Thrombocytopenia Causes


Cause Category	Primary Mechanism	Example Conditions	Key Distinctions
Decreased Production	Insufficient platelet creation in bone marrow.	Leukemia, chemotherapy, B12/folate deficiency, HIV, heavy alcohol use.	Often accompanied by other blood cell abnormalities (e.g., anemia).
Increased Destruction/Consumption	Platelets are destroyed or used faster than produced.	Immune thrombocytopenia (ITP), lupus, drug-induced issues, TTP, DIC, sepsis.	May be linked to autoimmune triggers, specific medications, or severe systemic illness.
Splenic Sequestration	Enlarged spleen traps excessive platelets.	Liver disease (cirrhosis), certain cancers leading to splenomegaly.	Often coincides with an underlying condition affecting the spleen.

Other Contributing Factors and Special Cases

COVID-19 has been linked to thrombocytopenia. Mechanical destruction of platelets can also occur with artificial heart valves or during procedures like bypass surgery.

Conclusion

Thrombocytopenia has a wide range of causes falling into categories of decreased production, increased destruction, or splenic sequestration. Accurate diagnosis requires a thorough medical evaluation. Identifying the specific cause is essential for effective treatment. For further information, consult resources like the National Heart, Lung, and Blood Institute (NHLBI) at nhlbi.nih.gov.

A Note on Seeking Medical Advice

This article is for informational purposes only and does not constitute medical advice. Consult a healthcare professional for diagnosis and treatment.

Frequently Asked Questions

The most common cause is often immune thrombocytopenia (ITP), an autoimmune disorder. However, mild, temporary low platelet counts can also frequently occur after a viral infection or during pregnancy.

Yes, many medications can cause thrombocytopenia. Heparin is a well-known example, but others include certain antibiotics, anti-seizure drugs, and quinine, which can trigger an immune-mediated destruction of platelets.

Liver disease, such as cirrhosis, often causes the spleen to become enlarged (splenomegaly). An enlarged spleen traps and sequesters more platelets than normal, leading to fewer circulating platelets. The liver also produces a hormone called thrombopoietin (TPO), and liver disease can decrease its production.

Yes, some rare genetic disorders, such as Wiskott-Aldrich syndrome and Fanconi anemia, can be inherited and result in a low platelet count. These are typically diagnosed in childhood.

Yes, infections are a significant cause. Viral infections like HIV and hepatitis C can directly affect bone marrow production. Severe bacterial infections (sepsis) can lead to widespread clotting and platelet consumption.

Mild thrombocytopenia is quite common during late pregnancy and is known as gestational thrombocytopenia. It is usually not serious and resolves on its own after delivery. However, it's crucial to rule out more serious pregnancy-related conditions like preeclampsia.

Diagnosing the cause involves a comprehensive approach by a healthcare provider. This includes reviewing medical history and medications, performing a physical exam, and running blood tests to check platelet count. A bone marrow biopsy might be needed if a bone marrow disorder is suspected.