Immune Deficiency Diseases (SCID)

What is it?
Immune Deficiency diseases are caused by the impairment of the immune system.

Inherited immune system disorders are also called primary immune deficiency disorders.

Mode of Inheritance?

The gene for the most common form of severe combined immunodeficiency is found on the X chromosome. Because females have two X chromosomes, if they have a mutation on one X chromosome, they have a spare X that can be used instead. Males have only one X chromosome and one Y chromosome. Since they do not have a spare X chromosome, they show signs of a mutation inherited on the X chromosome. Although a female who carries the mutation for SCID on one of her X chromosomes shows no signs of immunodeficiency, her sons and daughters have a 50% chance of inheriting the X chromosome with the mutation and a 50% chance of inheriting the normal X chromosome. The sons who inherit the mutant X chromosome will have SCID and the daughters who inherit the mutant X chromosome will be carriers like their mother. Carriers of SCID can be identified by mutation detection via laboratory test.

Clinical Description of ID?
While these disorders are rare, there are about 100 different types, which range from mild to severe. About 50,000 people in the United States have some type of inherited
immune system disorder.

Children with SCID develop symptoms in the first two to seven months. Typically they fail to gain weight and do not grow normally. They may have persistent diarrhea, upper respiratory symptoms and a fungal infection of the mouth and diaper area that doesn’t respond to typical treatments or medicines given for these symptoms.
A life threatening pneumonia can also be developed and often leads to the diagnosis of an immune system disorder. In normal individuals, this pneumonia does not lead to serious disease, but in SCID can be fatal if left untreated. Meningitis and bloodstream infections can also be seen.


The most common treatment for SCID is bone marrow transplantation, which has been successful using either a matched related or unrelated donor, or a half-matched donor, who would be either parent. The half-matched type of transplant is called haploidentical. David Vetter, the original "bubble boy", had one of the first transplantations but eventually died because of an unscreened virus in his newly transplanted bone marrow from his sister. Today, transplants done in the first three months of life have a high success rate. Physicians have also had some success with in utero transplants done before the child is born and also by using cord blood which is rich in stem cells.

The diseases can strike males and females of all ages, though they frequently present themselves early in life. The more severe immunodeficiency diseases are detected most frequently in children.

Primary Immunodeficiency diseases can go undetected because they do not have unique symptoms of their own. They appear as ordinary infections, often of the sinuses, ears, lungs, or intestines. Families and doctors are often unaware that the conditions they are dealing with are actually caused by a defect of the immune system. You can find the 10 warning signs that one may have an immune deficiency disease here.

People with an immune deficiency disease usually become very ill after being invaded my bacteria, while a healthy person will not get sick at all. Our bodies fight off infections everyday without us even knowing about it. People with an immune deficiency disease don’t have or have an incomplete immune system, so hey can not fight off bacteria, and get sick every time they are exposed to bacteria.

"Inherited immunodeficiency diseases." NCBI HomePage. Garland Science. 03 June 2009 <http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=imm.section.1494#1509>.
National Primary Immunodeficiency Resource Center. 03 June 2009 <http://www.info4pi.org/aboutPI/index.cfm?section=aboutPI&content=warningsigns>.
The SCID Homepage. 03 June 2009 http://www.SCID.net.