Is ITP a Primary Immunodeficiency? Explained

Immune thrombocytopenia (ITP) is a blood disorder that can cause bleeding and bruising. In most cases, ITP results from an autoimmune disorder — when the immune system mistakenly attacks healthy platelets, the cells that help your blood clot. ITP can also happen as a complication of other issues, including some types of primary immunodeficiency (PI).

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ITP itself isn’t a type of PI (also known as inborn errors of immunity). However, it can be a complication in people with PI as part of the disorder or as a related autoimmune problem. Keep reading to learn more about ITP, how it may be linked to PI, and common treatment options.

What Is Immune Thrombocytopenia?

In ITP, the immune system produces antiplatelet antibodies, which are a type of antibody (an immune protein that mistakenly targets the body’s own cells). This platelet destruction can cause platelet levels to drop too low, leading to symptoms such as:

• Petechiae (tiny red, purple, or brown spots caused by bleeding under the skin)
• Purpura (larger purple or red patches caused by bleeding from small blood vessels)
• Bruising, especially in areas where you haven’t been injured
• Bleeding, such as frequent nosebleeds, bleeding gums, blood in the urine or stool, and heavy menstrual periods
• Tiredness, often caused by anemia (low hemoglobin levels due to prolonged or repeated bleeding)

ITP may also be called immune thrombocytopenic purpura, idiopathic thrombocytopenic purpura, or autoimmune thrombocytopenia.

Types of Immune Thrombocytopenia

There are two main types of ITP — primary and secondary.

Primary ITP is diagnosed when you have a low platelet count without any known cause or underlying condition. About 80 percent of people diagnosed with ITP have primary ITP.

Secondary ITP happens when another medical condition triggers the immune system to attack platelets. Medical conditions and treatments linked to secondary ITP include:

• Autoimmune diseases such as systemic lupus erythematosus (lupus)
• Blood cancers, including chronic lymphocytic leukemia
• Chronic (long-term) infections like human immunodeficiency virus (HIV) and hepatitis C
• Some types of primary immunodeficiency
• Certain medications, including certain antibiotics, blood thinners, and anti-seizure drugs

ITP can also be classified based on how long it lasts:

• Acute ITP — Less than three months
• Persistent ITP — Three to 12 months
• Chronic ITP — More than 12 months

Why Does Immune Thrombocytopenia Happen in Primary Immunodeficiency?

Primary immunodeficiency is known for causing frequent or severe infections. However, PI can also lead to immune dysregulation, in which the immune response isn’t well controlled. Autoimmunity is a common form of immune dysregulation that often occurs in some types of PI. In autoimmunity, the immune system makes autoantibodies that attack healthy tissues. Autoimmunity is the main issue in some types of PI.

When autoimmunity affects the blood, it’s called autoimmune cytopenia — a group of conditions where the immune system attacks different types of blood cells. Besides ITP, in which platelets are targeted, autoimmune cytopenias include:

• Autoimmune hemolytic anemia — Affects red blood cells
• Autoimmune neutropenia — Affects neutrophils (a type of white blood cell)
• Evans syndrome — Occurs when two or more types of blood cells are attacked, such as both red blood cells and platelets

What Types of Primary Immunodeficiency Can Cause Immune Thrombocytopenia?

Several types of PI are associated with ITP, either as a common complication or an early sign.

Wiskott-Aldrich Syndrome

Wiskott-Aldrich syndrome (WAS), a rare form of PI, causes a range of health problems, including:

• Increased risk of infection
• Bleeding problems
• Eczema (an itchy rash)
• Autoimmune conditions, including ITP
• A higher risk of malignancy (cancer)

Thrombocytopenia is often one of the first signs of WAS. A key feature is a low platelet count along with small platelets that don’t work well, which can lead to serious bleeding symptoms. In a 2021 study, about 10 percent of people diagnosed with WAS had thrombocytopenia as their initial symptom.

Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is one of the most common types of PI. CVID leads to low levels of antibodies in the blood, although people with CVID usually have normal levels of B cells. The problem lies in how B cells mature into plasma cells, which produce antibodies. When this process is impaired, the immune system can’t make enough antibodies to fight infection.

Some people with CVID also have problems with their T cells, which increases the risk of complications such as autoimmunity and cancer.

Autoimmune Lymphoproliferative Syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is a type of PI in which white blood cells don’t die off when they should. Unlike other forms of PI, ALPS doesn’t significantly increase the risk of infection on its own. However, ALPS commonly causes autoimmune cytopenias, including ITP and autoimmune neutropenia (which can cause frequent infections).

Early signs of ALPS include frequent infections due to low neutrophils, along with bruising and frequent nosebleeds from low platelet counts.

How Is Immune Thrombocytopenia Diagnosed?

To diagnose ITP, doctors start with blood tests that measure blood cell levels. These tests typically include a complete blood count to check the number of red blood cells, white blood cells, and platelets. Your healthcare provider may also order a peripheral blood smear to look at blood cells and platelets under a microscope.

If your test results or symptoms suggest ITP, you may be referred to a specialist, such as a hematologist (doctor who treats blood disorders), an immunologist (immune system specialist), or an oncologist (cancer doctor). They may order more tests to identify the cause of your low platelet count.

Additional tests might include checking for autoantibodies or taking a bone marrow sample to see if your body is making platelets normally. If no underlying cause of ITP can be found, the diagnosis is primary ITP. If testing shows that PI is a possible cause, you’ll be diagnosed with secondary ITP.

How Is Immune Thrombocytopenia Treated Alongside Primary Immunodeficiency?

People with mild ITP symptoms may not need any treatment. Adults with ITP are more likely than children to have more severe symptoms that require treatment.

The goal of ITP treatment is to suppress the immune attack so the body can make more platelets and rebuild its supply. People with severe bleeding may also need a platelet transfusion to quickly replace platelet levels.

Corticosteroids (steroids) such as prednisone and dexamethasone are the most common first-line treatment. These drugs can temporarily block the antiplatelet antibodies. However, steroids can have side effects, so healthcare providers try to use the lowest effective dose for the shortest time.

Other treatment options may include:

• Intravenous immunoglobulin (IVIG) replacement therapy
• Immunosuppressive drugs, such as sirolimus and mycophenolate mofetil
• Chemotherapy drugs

ITP is often temporary, so many people need just short-term treatment — or none at all. However, if ITP is chronic or caused by a PI disorder, long-term treatment may be needed to prevent symptoms from coming back. Other treatments may be needed to manage the underlying immune condition.

What’s the Outlook for People With Immune Thrombocytopenia?

Most people with autoimmune cytopenias like ITP respond well to treatment. Regular follow-up with your healthcare team is important so they can monitor your platelet levels and adjust your care as needed.

If your platelet count stays low, your team may recommend precautions to help prevent serious bleeding. For example, you may be advised to avoid contact sports or wear protective gear (like a helmet) when riding a bike. However, most people can continue their usual daily activities.

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Have you or a loved one been diagnosed with primary ITP? Was bleeding one of the first symptoms? Share your story in the comments below.