WHAT IS ADENOSINE DEAMINASE DEFICIENCY? (c & f)
Adenosine Deaminase Deficiency is defined as an inherited disorder that may damage the immune system and causes severe combined immunodeficiency (also known as SCID). People diagnosed with SCID lack virtually all immune protection from bacteria, viruses, and fungi. The symptoms seen in ADA deficiency include pneumonia, chronic diarrhea, and widespread skin rashes. Children who are affected by this also grow much more slowly than healthy children and some may have developmental delay.
WHAT GENETIC ABNORMALITY IS RESPONSIBLE FOR THIS DISORDER? (a)
This disorder is caused by a change (mutation) in the ADA gene. The gene encodes an enzyme that is found in specialized white blood cells, those cells help prevent the body from ever getting an infection.
ON TO WHICH CHROMOSOMES HAS THE GENETIC ABNORMAILTY BEEN MAPPED? (b)
I actually couldn't find a clear answer to this, so here's a big paragraph of stuff I think might have to do with the question and answer:
"Genetic and biochemical characterization of ADA in SCID and the ADA tissue-specific isozymes in normal human cells indicates that additional genes, besides the ADA structural gene on chromosome 20, are involved in ADA expression. Human chromosome 6 encodes a gene, ADCP-1, whose presence is necessary for the expression of an ADA-complexing protein in human-mouse somatic cell hybrids [Koch, G. & Shows, T. B. (1978) Proc. Natl. Acad. Sci. USA 75, 3876-3880]. We report the identification of a second gene, ADCP-2, on human chromosome 2, that is also involved in the expression of the ADA-complexing protein. The data indicate that these two ADCP genes must be present in the same cell for that cell to express the complexing protein. Human-mouse somatic cell hybrids, in which the human parental cells were fibroblastss from an individual with ADA-deficient SCID, also required human chromosomes 2 and 6 to express the ADA-complexing protein, indicating that neither ADCP-1 nor ADCP-2 is involved in the ADA deficiency in SCID. The SCID-mouse hybrid cells expressed no human ADA even when human chromosome 20 had been retained. The deficiency of human ADA in these hybrids maps to human chromosome 20, and therefore is not due to the repression or inhibiton of ADA or its product by unlinked genes or gene products. We propose that the expression of the polymeric ADA tissue isozymes in human cells requires at least three genes: ADA on chromosome 20, ADCP-1 on chromosome 6, and ADCP-2 on chromosome 2. A genetic scheme is presented and the different genes involved in ADA expression and their possible functions are discussed." (G Koch and T B Shows,Somatic cell genetics of adenosine deaminase expression and severe combined immunodeficiency disease in humans)
HOW IS THE DISORDER DIAGNOSED? (d)
In most cases, signs and symptoms of adenosine deaminase deficiency develop typically before 6 months of age. The affected babies are usually started off being diagnosed with severe combined immunodeficiency (SCID), a condition characterized by a reduced/absent immune response. If the signs and symptons start increasing dramatically, like they do in ADA, then what was once SCID would be diagnosed as ADA. There is no routine genetic test, it's easy to spot if someone has ADA.
WHAT TREATMENT OPTIONS ARE THERE FOR THIS DISORDER? (e)
It's hard finding a direct solution to this disorder is further complicated by the fact that ADA deficiency is not solely an immune defect, unlike other SCID forms, and the systemic manifestations, which can be of major clinical consequences, must also be managed. However, unlike other SCID forms, there are 2 other treatment options that are available for ADA-SCID, including enzyme replacement therapy (ERT) with pegylated bovine ADA (Pegadamase, Adagen, or PEG-ADA) and autologous HSC gene therapy (GT).