Severe combined immunodeficiency due to adenosine deaminase deficiency (Severe combined immunodeficiency due to adenosine deaminase deficiency) - Gen ADA.
Severe combined immunodeficiency due to adenosine deaminase deficiency is an inherited disorder that affects the immune system. Affected individuals have virtually no immune protection against all bacteria, viruses and fungi. These people are prone to recurrent and persistent infections that can be serious or life - threatening. These infections are usually caused by organisms "opportunists" who usually do not cause disease in people with normal immune systems.
The main symptoms of the disease include pneumonia, chronic diarrhea and generalized rashes. Affected children also grow much more slowly than healthy and some children have developmental delays. Most affected individuals are diagnosed in the first 6 months of life. Without treatment, usually newborn infants do not survive beyond 2 years of age. In about 10% to 15% of cases, the onset is delayed at 6 to 24 months old or even into adulthood. When the disease is late onset tends to be less severe, causing recurrent infections mainly upper respiratory and ear. Over time, affected individuals may develop chronic lung damage, malnutrition and other health problems.
This process is due to changes in the ADA gene, located on the long arm of chromosome 20 (20q13.12). This gene encodes the enzyme adenosine deaminase. This enzyme is found throughout the body, but is more active on lymphocytes. These cells protect the organism against potentially harmful invaders, such as bacteria and viruses, by producing antibodies or directly attacking infected cells. The function of the enzyme adenosine deaminase to eliminate a molecule of deoxyadenosine, which is generated when the DNA is decomposed. Adenosine deaminase converts deoxyadenosine, which can be toxic to cells, a molecule that is not toxic deoxyinosine.
They have identified more than 70 mutations in the ADA gene in affected individuals. Mutations in the ADA gene reduce or eliminate the activity of adenosine deaminase and allow the accumulation of deoxyadenosine at concentrations that are toxic to cells. Immature lymphocytes in the thymus are particularly vulnerable to a toxic buildup of deoxyadenosine. These cells die before they can mature to help fight infection. The number of lymphocytes in other lymphoid tissues are also greatly reduced. Loss of cells that fight infection leads to the signs and symptoms of SCID.
This disease is inherited in an autosomal recessive pattern, that is, both copies of the gene in every cell must have mutations for alteration is expressed. The parents of an individual with an autosomal recessive disease have a copy of the mutated gene, but usually show no signs and symptoms of the disease.
Tests in IVAMI: in IVAMI perform detection of mutations associated with severe combined immunodeficiency due to adenosine deaminase deficiency, by complete PCR amplification of the exons of the ADA gene, and subsequent sequencing.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).