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Immune deficiency diseases occur when a person’s immune system is defective or impaired. This results in the body’s inability to properly fight off disease and infection. There are different types of immunodeficiency disorders that are categorized into two main types. These types of immune deficiency diseases include congenital immunodeficiency disorders, which are considered primary, and acquired immunodeficiency disorders, which are secondary. The most common immune deficiency diseases include common variable immunodeficiency (CVID), severe combined immunodeficiency (SCID), acquired immunodeficiency syndrome (AIDS), severe acute respiratory syndrome (SARS) and DiGeorge Syndrome.
Although acquired immunodeficiency disorders are more common than congenital disorders, the congenital disorders are present in the body at the time of birth. Thus, they are a result of genetic defects and are considered innate. These immune deficiency diseases might include SCID and CVID, such as forms of pneumonia, lupus and influenza.
Acquired immunodeficiency diseases commonly result from immunosuppressant drugs that are used to treat serious disorders and inhibit the immune system. Chemotherapy and radiation can also lead to immunodeficiency disorders. Acquired immunodeficiency disorders most often occur as a result of other diseases or from the complication of other disorders.
Types of immune deficiency diseases that lead to acquired immunodeficiency disorders include the human immunodeficiency virus (HIV), which causes AIDS. Other disorders include malnutrition, types of cancers, measles, chicken pox, chronic hepatitis and bacterial and fungal infections. SARS is another form of acquired immunodeficiency disorder that appeared in China and Canada in 2003.
The primary type of immune deficiency diseases are congenital immunodeficiency disorders, and they occur when defects are present in either the b-cells — also called b-lymphocytes, which are produced in the bone marrow — the t-cells or t-lymphocytes, which mature in the thymus. Congenital disorders also can occur when defects are found in both b and t cells. There are several types of primary immunodeficiencies, and a common one is Bruton’s agammaglobulinemia, also known as X-Linked agammaglobulinemia (XLA).
A type of humoral, or specific, immunity disorder, XLA occurs when there is a defect or absence of b-cells, where the immune system is unable to produce antibodies. People suffering from this disorder fall victim to infections of the skin, throat, ear and lungs. Found only in males, it is caused by a defect on the X chromosome.
Hyper-igm Syndrome is another humoral immunodeficiency that occurs and is a result of defects in the b-cells and deoxyribonucleic acid (DNA) repair. It is found in other antibody deficiency syndromes, such as CVID. Another type of b-cell deficiency, the production of immunoglobin in CVID is decreased, and antibody response is impaired. This disorder develops between ages 10-20, and people who have CVID suffer multiple infections and might experience rheumatoid arthritis and anemia. Eventually, they might also develop cancer.
Often fatal, t-lymphocyte deficiencies occur when t-cells fail to mature, resulting in an immune system that is particularly susceptible to infection from viruses, bacteria and fungi. A t-cell deficiency, DiGeorge Syndrome develops in the fetus when a certain chromosome is deleted. Children are often born with no thymus or one that is underdeveloped and often have physical abnormalities such as wide-set eyes and a low-set jawbone or ears.
Yet another congenital immunodeficiency is when both b-cells and t-cells are affected. Severe combined immunodeficiency (SCID) is caused by defective b and t lymphocytes and impairs cellular immune responses. Discovered within the first year, children who have SCID suffer from fungal infections such as thrush, and without a bone marrow transplant, they will die during their first year of life.