Immunodeficiency occurs when the body's immune system is impaired, making an individual more susceptible to frequent and severe illnesses. Primary immunodeficiency is present at birth, occurring as a result of genetic abnormalities. Secondary or acquired immunodeficiency, on the other hand, develops later on in life, caused by certain drugs, chronic medical diseases or undernutrition.
Genetic Abnormalities
A number of inheritable genetic defects can cause an infant to be born with immunodeficiency. According to the Merck Manuals Online Medical Library, genetic causes of primary immunodeficiency are usually linked to the X chromosome, meaning that boys are more likely to inherit the problem. These abnormalities cause one of several components of the immune system, including B lymphocytes, T lymphocytes, phagocytes, bacteria fighting proteins or certain antibodies, to be defective, be present in abnormally low numbers or be missing altogether.
The Penn State Milton S. Hershey Medical Center College of Medicine notes that some babies may be born with severe combined immunodeficiency disease, or SCID, a condition caused by a defect in both B lymphocytes--cells that make antibodies--and T-lymphocytes--cells responsible for helping with the immune response by identifying foreign bacteria or substances. According to KidsHealth.org, the most common inherited cause of immunodeficiency is IgA deficiency--a condition in which the body fails to produce enough of the IgA antibody, rendering the affected person more susceptible to respiratory infections and colds.
Chronic Medical Disorders
According to the Penn State College of Medicine, disease is the most common cause of secondary or acquired immunodeficiency. Chronic blood disorders like sickle cell anemia and leukemia, Down syndrome, certain cancers such as lung cancer and brain cancer, hepatitis, diabetes and inflammatory diseases like lupus and rheumatoid arthritis may all induce immunodeficiency over time. Certain infections can also cause immunodeficiency, including measles, cytomegalovirus and Epstein-Barr infections and human immunodeficiency virus, commonly called HIV, infections, according to Merck Manuals.
Medications
KidsHealth.org explains that drugs that suppress the immune system that are often given to treat cancer can also attack healthy immune cells, causing secondary immunodeficiency by destroying the body's ability to fight off infection and disease. Merck Manuals adds that chemotherapy and radiation treatments for cancer, as well as medications such as corticosteroids that are used to treat autoimmune and inflammatory diseases like rheumatoid arthritis, can also lead to immunodeficiency. Other medications shown to induce immunodeficiency include anti-seizure medications like phenytoin and valproate.
Undernutrition
Individuals who fail to consume enough food and proper nutrients may be at risk for acquiring immunodeficiency. According to Merck Manuals, those whose weight drops to below 70 to 80 percent of their recommended weight can damage their immune systems and ability to fight off infection.
