Causes and Risk Factors for Thrombocytopenia

Thrombocytopenia is diagnosed when the number of platelets in the blood is low.

Platelets are the cells in the blood that clot the blood and heal blood vessel walls in the event of bleeding. Having too few platelets can lead to bruising or active bleeding.

Normal platelet counts are 150,000 to 450,000 per microliter of blood and can be discovered during a simple blood test. If a platelet count falls below 150,000 per microliter of blood, it is called thrombocytopenia.

This article discusses the causes and risk factors for thrombocytopenia.

Common Causes

Thrombocytopenia can be caused by problems with the bone marrow not making enough platelets or by the immune system destroying platelets inappropriately, which is called immune-mediated thrombocytopenia.

Sometimes platelets will sequester, or stay in the spleen and not out in the circulating blood.

Thrombocytopenia can also be caused by side effects of medications, such as chemotherapy.  

Bone Marrow Suppression

Bone marrow is the tissue inside of bones that makes white blood cells, red blood cells, platelets, and plasma. If the bone marrow is not working properly, it may not make enough platelets. Some conditions that may keep bone marrow from working properly include:

• Cancer: Certain cancers such as leukemia or lymphoma may develop in the bone marrow and prevent platelets from being made normally.
• Myelodysplastic syndrome: This is a group of disorders in which the bone marrow fails to make blood cells properly.
• Chemotherapy: Many chemotherapy medications used to treat cancer can cause suppression of the bone marrow and lead to low platelets.
• Viral infections: Many viruses can cause the bone marrow to function improperly. Some of these viruses include cytomegalovirus, Epstein-Barr virus, HIV, and rubella.
• Nutrient deficiency: Low levels of vitamin B12 or folate can cause decreased platelet counts.
• Chemical exposure: Exposure to some chemicals such as pesticides can decrease platelet counts.

Immune-Mediated Thrombocytopenia

• Autoimmune disorders: Some autoimmune disorders may cause the immune system to destroy platelets, causing low levels in the blood. It is often unknown why the immune system destroys the platelets.
• Medications: Certain medications carry the risk of potentially causing the body to destroy its own platelets. Some of these medications include Heparin, sulfa antibiotics, and rifampin.
• Infection: Low platelets may develop as they are consumed by the immune system during a viral or bacterial infection.

Spleen Sequestration

Normally, about one-third of the platelets in the body will rest in the spleen. However, sometimes certain conditions cause the spleen to hold on to a greater number of platelets. Some of these conditions include:

• Liver disease: Diseases such as cirrhosis or portal hypertension can cause the liver to enlarge and hold on to too many platelets.
• Cancers or other bone marrow disorders: Sometimes certain cancers or bone marrow dysfunction can cause the spleen to enlarge.

Pregnancy

Low platelet counts can be a fairly common finding during the last trimester of pregnancy. This can happen without a known cause, but may develop due to other pregnancy-related complications such as preeclampsia or HELLP syndrome.

Genetics

Certain genetic conditions can lead to the development of low platelets. 

X-Linked Thrombocytopenia

In this genetic disorder, platelets are smaller than normal and platelet counts are less than normal. People with X-linked thrombocytopenia often have easy bruising, and sometimes they may have eczema as well.

Wiskott-Aldrich Syndrome

This genetic disorder is only found in males, and is associated with smaller-than-normal platelets along with abnormalities in certain immune system cells. This usually develops by the time a child turns 3 years old.

Congenital Amegakaryocytic Thrombocytopenia

This genetic disorder is typically discovered within the first days of an infant’s life, and the infant develops bleeding due to critically low platelet counts.

Lifestyle Risk Factors

Alcohol Use

Heavy and frequent alcohol use can directly decrease platelet counts in the blood. This is also often associated with dietary deficiencies such as B12 or folate, which can also decrease platelet counts.

Chemical Exposure

Environmental exposure to certain chemicals such as pesticides and arsenic can decrease platelet counts in the blood.

A Word From Verywell

Thrombocytopenia, or low platelet counts, can be caused by a variety of conditions. If you have one of the conditions listed above or have other concerns that you may have low platelets, contact your healthcare provider to have this evaluated. A simple blood test can find out if you have normal or less-than-normal platelet counts.