Adenosine deaminase (ADA) deficiency is an inherited disorder that leads to severe combined immunodeficiency (SCID), damaging the immune system and leaving individuals highly susceptible to infections from bacteria, viruses, and fungi.
Commonly caused by “opportunistic” organisms, these infections pose serious or life-threatening risks. The primary symptoms include pneumonia, chronic diarrhea, widespread skin rashes, stunted growth, and possible developmental delays, particularly in affected children. Typically diagnosed with SCID within the first 6 months of life, most individuals with ADA deficiency face a poor prognosis if left untreated, with survival rates rarely extending past age 2. However, in a small percentage of cases (10% to 15%), immune deficiency may manifest later, between 6 and 24 months of age or even into adulthood. In these later-onset cases, the severity of the immune deficiency is reduced, leading mainly to recurrent upper respiratory and ear infections. Nonetheless, over time, chronic lung damage, malnutrition, and other health complications may develop in affected individuals. Various treatment options exist for ADA deficiency.
ADA is caused by pathogenic (disease-causing) variants in the ADA gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition.
Other names for this condition are ADA-SCID, adenosine deaminase deficient severe combined immunodeficiency, SCID due to ADA deficiency, severe combined immunodeficiency due to ADA deficiency, and severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency
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Revised July 2023
