The environment teems with potentially infectious microbes. Human survival depends on the immune system's capacity to fight infection if a microbe penetrates the surface-level body defenses. Acquired immunodeficiency syndrome, or AIDS, leaves the body lacking immune system protection due to destruction of immune cells by the human immunodeficiency virus. Similarly, several genetic disorders can also cause abnormalities that render the body immunodeficient.
Common Variable Immunodeficiency
Insufficient production of immunoglobulins characterizes common variable immunodeficiency. Immunoglobulins, also known as antibodies, are proteins made by the immune system that tag invading organisms for immune system destruction. These proteins prove critically important in defending against bacteria. Thus, people with common variable immunodeficiency exhibit exceptional vulnerability to bacterial infections. In a review article published electronically by Gene Reviews, Dr. Andrew Scharenberg and colleagues note that people with common variable immunodeficiency suffer from serial bacterial infections of the sinuses, lungs, skin and eyes. Increased susceptibility to bloodstream infections and meningitis poses a potentially life-threatening risk for those with the illness. In contrast to other genetic immune system disorders, common variable immunodeficiency typically does not present until young adulthood.
Severe Combined Immunodeficiency
Immune system functions depend on two primary cell types, T cells and B cells. Severe combined immunodeficiency disorders are rare conditions characterized by a lack of T cells. Without the help of T cells, B cells become largely nonfunctional. Thus, those with severe combined immunodeficiency have no appreciable immune system function. The University of Utah Genetic Science Learning Center explains that infants with this disorder develop serial infections, typically leading to diagnosis in the first few months of life. Children with severe combined immunodeficiency require a protective environment to limit contact with potentially disease-causing microbes. Bone marrow transplantation provides children with severe combined immunodeficiency an opportunity for a functioning immune system and a markedly enhanced quality of life.
Chediak-Higashi Syndrome
White blood cells called phagocytes normally ingest and kill invading bacteria. With Chediak-Higashi syndrome, a genetic abnormality impairs the bacterial killing ability of the phagocytes. In a review article on Chediak-Higashi syndrome published electronically by Gene Reviews, Dr. Wendy Introne and colleagues report that those with the disorder suffer frequent bacterial skin and respiratory infections. Other abnormalities associated with Chediak-Higashi syndrome include albinism--lack of color of the eyes, hair and skin--and defects in the blood clotting system. A rapidly progressive stage of the illness causes enlargement of the liver and spleen, fever, and a decrease in the blood cell and platelet counts. Onset of the accelerated phase of the illness proves ominous. According to "The Merck Manual for Healthcare Professionals," most patients die within two to three years after entering this stage of the illness.
References
- Merck Manual for Healthcare Professionals: Common Variable Immunodeficiency
- Gene Reviews: Common Variable Immunodeficiency
- Merck Manual for Healthcare Professionals: Severe Combined Immunodeficiency
- University of Utah Genetic Science Learning Center: Severe Combined Immunodeficiency
- Merck Manual for Healthcare Professionals: Chediak-Higashi Syndrome
