Immune Deficiency

Overview

Immune deficiency, also called immunodeficiency, occurs when one or more parts of the immune system are missing or do not work as they should. The immune system normally defends the body against bacteria, viruses, fungi, and other germs. When it is weakened, infections happen more often, last longer, are more severe, or are caused by unusual organisms.

Immune deficiencies fall into two broad groups. Primary immune deficiencies are usually inherited and present from birth, although they may not be recognized until later. Secondary, or acquired, immune deficiencies develop later in life from another cause, such as an infection, a medication, or a chronic illness. Treatment depends on the type and cause.

Symptoms

The hallmark of immune deficiency is a pattern of infections that is more frequent, severe, or unusual than expected. Signs may include:

• Frequent infections, such as recurring sinus, ear, lung, or skin infections.
• Severe or hard-to-treat infections that need repeated or prolonged treatment.
• Infections from unusual organisms that rarely affect healthy people.
• Slow recovery from infections.
• Other features such as poor growth in children, persistent diarrhea, or certain autoimmune problems.

Because everyone gets occasional infections, the concern is a clear pattern of repeated, serious, or unusual illness over time.

Causes

Immune deficiency has many possible causes, grouped into two main types:

• Primary immune deficiencies: Inherited conditions in which part of the immune system fails to develop or function normally. There are many forms, ranging from mild to severe.
• Secondary (acquired) immune deficiencies: Caused by something outside the immune system itself, including certain infections such as HIV/AIDS, medications such as chemotherapy or long-term steroids, poor nutrition, diabetes, certain cancers, and the removal of the spleen.

Secondary causes are far more common than inherited ones.

Risk Factors

• A family history of primary immune deficiency
• HIV infection or other immune-weakening infections
• Treatment with chemotherapy, immune-suppressing drugs, or long-term steroids
• Diabetes or other chronic illnesses
• Malnutrition
• Having the spleen removed
• Older age, which is linked to a gradual decline in immune function

Diagnosis

Diagnosis starts with a careful history of infections and may involve specialized testing.

• Medical and family history: Looking at the pattern, frequency, and type of infections.
• Blood tests: To count immune cells, measure antibody (immunoglobulin) levels, and assess immune function.
• Response to vaccines: Checking whether the body makes antibodies after immunization.
• Targeted tests: Including genetic testing for suspected primary immune deficiencies and tests for underlying conditions such as HIV or diabetes.

Treatment

Treatment depends on the type and cause of the immune deficiency and aims to prevent and control infections.

• Treating infections promptly: Often with antibiotics, antivirals, or antifungals, and sometimes longer or preventive courses.
• Immunoglobulin replacement: For some antibody deficiencies, regular infusions of antibodies help protect against infection.
• Treating the underlying cause: Such as controlling HIV, managing diabetes, or adjusting immune-suppressing medications when possible.
• Vaccination and preventive measures: Guided carefully, since some vaccines are not safe for severely affected people.
• Advanced therapies: Such as stem cell transplant for certain severe inherited forms.

Care is usually long term and coordinated with a specialist, often an immunologist, who tailors treatment to the specific type of immune deficiency. Regular follow-up helps track infections, adjust treatment, and catch complications early. With the right plan, many people with immune deficiency can live full and active lives while keeping infections under control.

Prevention

Inherited immune deficiencies cannot be prevented, but you can lower the risk of acquired forms and reduce infections:

• Practice good hand hygiene and avoid people who are sick when possible
• Keep recommended vaccinations up to date, as advised by your clinician
• Manage chronic conditions such as diabetes well
• Eat a balanced diet and avoid malnutrition
• Take immune-suppressing medications only as prescribed
• Seek prompt treatment for infections

When to See a Doctor

See a doctor if you or your child have a pattern of frequent, severe, or unusual infections, infections that do not clear with standard treatment, or poor growth with repeated illness. Seek emergency care for signs of a serious infection, such as:

• High fever with confusion, severe weakness, or difficulty breathing
• A rapidly spreading skin infection
• Signs of sepsis, including a very fast heartbeat, low blood pressure, or feeling extremely unwell

Related Topics

Frequently Asked Questions

References

1. National Institute of Allergy and Infectious Diseases (NIAID). Primary Immune Deficiency Diseases.
2. MedlinePlus, U.S. National Library of Medicine. Immunodeficiency disorders.
3. Centers for Disease Control and Prevention (CDC).
4. Mayo Clinic. Primary immunodeficiency — Symptoms and causes.