Immunodeficiency disorders occur when the body's immune response is reduced or absent.

See also: Autoimmune disorders

The immune system is made up of lymphoid tissue in the body, which includes the bone marrow, lymph nodes, thymus, tonsils, and parts of the spleen and gastrointestinal tract.

The immune system helps protect the body from harmful substances called antigens. Examples of antigens include bacteria, viruses, toxins, cancer cells, and foreign blood or tissues from another person or species.

When the immune system detects an antigen, it responds by producing antibodies that destroy the harmful substances. The immune system response also involves a process called phagocytosis. During this process, certain white blood cells swallow and destroy bacteria and other foreign substances.

Immune system disorders occur when the immune system does not fight tumors or harmful substances as it should. The immune response may be overactive or underactive.

Immunodeficiency disorders may affect any part of the immune system. Most commonly, such a condition occurs when specialized white blood cells called T or B lymphocytes (or both) do not work as well as they should, or when your body doesn't produce enough antibodies.

Inherited immunodeficiency disorders that affect B cells include:

• Hypogammaglobulinemia, which usually causes mild to moderate respiratory infections
• Agammaglobulinemia, which results in frequent severe infections and is often deadly

Inherited immunodeficiency disorders that affect T cells may cause increased susceptibility to fungi, resulting in recurring Candida (yeast) infections. Inherited combined immunodeficiency affects both T cells and B cells. It may be deadly within the first year of life if it isn't treated early.

People are said to be immunosuppressed when they have an immunodeficiency disorder due to medicines that affect the immune system (such as corticosteroids). Immunosuppression is also a common side effect of chemotherapy.

Acquired immunodeficiency may be a complication of diseases such as HIV infection and AIDS. Malnutrition, particularly with lack of protein, and many cancers may also cause immunodeficiency.

People who have had their spleen removed are at higher risk for infection by certain bacteria that the spleen would normally help fight. Patients with diabetes are also at higher risk for certain infections.

Increasing age reduces the effectiveness of the immune system to some degree. Immune system tissues (particularly lymphoid tissue such as the thymus) shrink, and the number and activity of white blood cells drop.

The following conditions and diseases can result in an immunodeficiency disorder:

• Ataxia-telangiectasia
• Chediak-Higashi syndrome
• Combined immunodeficiency disease
• Complement deficiencies
• DiGeorge syndrome
• Hypogammaglobulinemia
• Job syndrome
• Leukocyte adhesion defects
• Panhypogammaglobulinemia
  • Bruton disease
  • Congenital agammaglobulinemia
• Selective deficiency of IgA
• Wiscott-Aldrich syndrome

The symptoms vary with the specific disorder.

Your doctor might think you have an immunodeficiency disorder is present if you have:

• Persistent, recurrent infections; or
• Severe infection by microorganisms that do not usually cause severe infection

Other signs include:

• Poor response to treatment
• Delayed or incomplete recovery from illness
• Certain types of cancers (such as Kaposi's sarcoma or non-Hodgkin's lymphoma)
• Certain infections (including some forms of pneumonia or recurrent fungal yeast infections)

Tests used to help diagnose an immunodeficiency disorder may include:

• Antibody/immunoglobulin levels
• Complement levels or other tests to measure substances released by the immune system
• T (thymus derived) lymphocyte count
• White blood cell count

The goal of treatment is to prevent infections and treat any disease and infections that do develop.

If you have a weakened immune system, you should avoid contact with persons who have infections or contagious disorders. This may include avoiding people who have been vaccinated with live virus vaccines within the past two weeks.

If you develop an infection, your doctor will treat you aggressively. This may involve long-term use of antibiotic or antifungal medications and preventive (prophylactic) treatments.

Interferon is used to treat viral infections and some types of cancer. It is an immunostimulant drug, a medicine that makes the immune system work better.

Persons with HIV and AIDS may take combinations of drugs to reduce the amount of virus in their immune systems, thus improving their immunity.

Patients undergoing a planned splenectomy should be vaccinated two weeks prior to the surgery against encapsulated organisms such as Streptococcus pneumonia and Hemophilus influenzae.

Bone marrow transplant may be used to treat certain immunodeficiency conditions.

Passive immunity (administration of antibodies produced by another person or animal) may occasionally be recommended to prevent illness after exposure to a microorganism.

Patients with hypogammaglobulinemia are treated with periodic immunoglobulin infusions through a vein to raise blood immunoglobulin levels towards the normal range.

Some immunodeficiency disorders are mild and result in occasional illness. Others are severe and may be fatal. Immunosuppression that results from medications is often reversible once the medication is stopped.

• Disease development
• Frequent or persistent illness
• Increased risk for certain cancers or tumors
• Opportunistic infections

Call your health care provider immediately if you are on chemotherapy or corticosteroids (such as prednisone, Medrol, or Decadron) and you develop a fever greater than 100.5 degrees Fahrenheit or have cough with shortness of breath.

Go to the emergency room if you have a stiff neck and headache with the fever.

Contact your health care provider if you have recurrent yeast infections or oral thrush.

There is no known prevention for congenital immunodeficiency disorders. Safe sex practices and avoiding the sharing of body fluids may help to prevent HIV infection and AIDS. Good nutrition may prevent acquired immunodeficiency caused by malnutrition.

Bonilla FA, Bernstein IL, Khan DA, et al. Practice parameter for the diagnosis and management of primary immunodeficiency. Ann Allergy Asthma Immunol. 2005;94:S1-S63.