Running head GENETIC DISORDE R RESEARCH SEVERE C Essays - Medicine

Running head: GENETIC DISORDE R RESEARCH: SEVERE COMBINED IMMUNODEFICIENCY Genetic Disorder Research: Severe Combined Immunodeficiency Spring Valley High School Biology 1 CP November 3, 2011 Genetic Disorder Research: Severe Combined Immunodeficiency Inherited immune disorders are also called primary immune deficiency disorders. They are caused by a mistake in a gene that affects the immune system. Genes carry an inherited code of instructions that tell the body to make all the cells and proteins in the body. Severe Combined Immunodeficiency (SCID) is a group of very rare-and potentially fatal-inherited disorders related to the immune system. This disorder results from a heterogeneous group of genetic conditions. In SCID, there is a fault in the specialized white blood cells (T and B cells) that fight off viruses, bacteria and fungi. The B cells make antibodies that are proteins that attach to unrecognized cells and mark them to be attacked and destroyed. T cells direct B cells to make antibodies against other cells. These cells also direct the rest of the immune system when to attack and also when to stop. They help in the attack as well. SCID is sometimes called "Bubble Boy Disease". "Bubble Boy Disease" is named aft er David Vetter, a boy from the 1970's, who lived in a plastic bubble for 12 years after being diagnosed with SCID. The immune system is supposed to fight off attacks from dangerous bacteria and viruses on a regular basis. However, people with SCID have a problem in their immune system that leaves them defenseless to dangerous infections. There are many different types of SCID. All forms of SCID are inherited. Some types of SCID appear when the gene is inherited by both parents. These occur in both males and females. Half of the SCID cases are linked to the X chromosome, and is passed on by the mother. The most common form of SCID has a X-linked pattern of inheritance that's recessive. It is referred to as X-linked SCID. There is also a mutation in JAK3 on chromosome 19 that can also result in SCID. When a gene is on the X chromosome, males are often more affected than females. Males don't have a second X chromosome to take place for the defected one. They only need to inherit one bad copy of the gene to have the symptoms of the disorder. Females have two X chromosomes that makes having SCID somewhat ineffective. If one of the X chromosomes becomes defective, there is still a healthy pair left. Females also don't get symptoms of the disorder, but they will carry the gene and can pass it to their children. Ano ther form of SCID is a lack of the enzyme adenosine deaminsase ( ADA ). This is coded for by a gene on chromosome 20. The substrates for this enzyme grow in the cells. Immature lymphoid cells (in the immune system) are sensitive to toxic effects of the unused substrates; they fail to reach maturity. This results in the immune system of the person to be unable to function properly. About 1 in every 100,000 babies is born with SCID. Doctors can diagnose SCID to the baby before it is born by removing and testing cells from the placenta, or by removing and testing a sample of the fluid surrounding the baby . Symptoms of SCID usually show up in the first few months of their life. Most babies are diagnosed with SCID in the first six months. Infants with SCID tend to appear with infections that are secondary to the lack of T-cell function. The immune system cannot protect the body of a baby, causing babies with this disorder to get one infection after another. Their infections may be frequent, severe, long-lasting or just hard to treat. Some of the bacterial infections may be life-threatening, such as pneumonia, meningitis, and sepsis. Babies also get diarrhea that doesn't go away. Babies with SCID also don't gain weight or grow at a normal rate. SCID patients often don't respond to the medicines used to treat bacterial infections. U nlike people with normal functioning immune systems, people with SCID may suffer more from ear infections, sinus infections, chronic cough, and rashes on skin. It is better to have