Severe combined immunodeficiency syndrome (SCID) is characterized by the lack of

Question

Severe combined immunodeficiency syndrome (SCID) is characterized by the lack of an immune response to infectious diseases. Many SCID patients have a deficiency of adenosine deaminase (see figure in the appendix), which catalyzes the deamination of adenosine to produce inosine. The enzyme deficiency increases dATP levels but decreases the levels of other deoxynucleotides, thereby inhibiting DNA replication and cell division in certain rapidly dividing cells. Explain how an adenosine deaminase deficiency affects the levels of deoxynucleotides.

Explanation / Answer

HI

Adenosine deaminase deficiency, also called ADA deficiency or ADA-SCID, is an autosomal recessivemetabolic disorder that causes immunodeficiency. It occurs in fewer than one in 100,000 live births worldwide.It accounts for about 15% of all cases of severe combined immunodeficiency (SCID). Only 3% of children are born with this gene.ADA deficiency may be present in infancy, childhood, adolescence, or adulthood. Age of onset and severity is related to some known genotypes associated with the disorder.

Pathophysiology:ADA deficiency is due to a lack of the enzyme adenosine deaminase. This deficiency results in an accumulation of deoxyadenosine, which, in turn, leads to:

Because T cells undergo proliferation and development in the thymus, affected individuals typically have a small, underdeveloped thymus. As a result, the immune system is severely compromised or completely lacking.

Genetics :Adenosine deaminase deficiency has an autosomal recessive pattern ofinheritance.

The enzyme adenosine deaminase is encoded by a gene on chromosome 20. ADA deficiency is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome (chromosome 20 is an autosome), and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.

Treatments include:

On September 14, 1990, the first gene therapy to combat this disease was performed by Dr. William French Anderson on a four year old girl, Ashanti DeSilva, at the National Institutes of Health, Bethesda, Maryland, U.S.A.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.