Immunodeficiency, also known as immunocompromisation, is a state in which the immune systems ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that affect the patients immune system. Examples of these extrinsic factors include HIV infection and environmental factors, such as nutrition. Immunocompromisation may also be due to genetic diseases/flaws such as SCID. In clinical settings, immunosuppression by some drugs, such as steroids, can either be an adverse effect or the intended purpose of the treatment. Examples of such use is in organ transplant surgery as an anti-rejection measure and in patients with an overactive immune system, as in autoimmune diseases. Some people are born with intrinsic defects in their immune system, or primary immunodeficiency.A person who has an immunodeficiency of any kind is said to be immunocompromised. An immunocompromised individual may particularly be vulnerable to opportunistic infections, in addition to normal infections that could affect anyone. It also decreases cancer immunosurveillance, in which the immune system scans the bodys cells and kills neoplastic ones. They are also more susceptible to infectious diseases owing to reduced protection afforded by vaccines. Types
By affected component
Humoral immune deficiency (including B cell deficiency or dysfunction), with signs or symptoms depending on the cause, but generally include signs of hypogammaglobulinemia (decrease of one or more types of antibodies) with presentations including repeated mild respiratory infections, and/or agammaglobulinemia (lack of all or most antibody production) which results in frequent severe infections and is often fatal.
Costello syndrome is caused by mutations in HRAS. Mutations that cause Noonan syndrome have been found in PTPN11 and SOS1.The relative severity of CFC when compared to Noonan syndrome may reflect the position in the biochemical pathway occupied by the affected genes. Shp2, the protein product of the PTPN11 gene, appears to regulate the MAP kinase pathway at or above the level of SOS1. SOS1 in turn regulates the activities of RAS, RAF, MEK, ERK, and p90RSK. SOS1 has been demonstrated to be a target of negative feedback by ERK and p90RSK.Thus, any activating mutation downstream of SOS1 may be subject to less regulation that might mitigate the consequence of such mutations, giving rise to the phenotypic differences seen between these syndromes. Diagnosis
Management
References
External links

CFC Syndrome at Genetics Home Reference
GeneReview/UW/NIH entry on CFC