What is ADA2 Protein Deficiency?
Adenosine deaminase 2 (ADA2) deficiency is a type of genetic disorder where the patient has a deficiency or reduced levels of an enzyme or protein called adenosine deaminase 2 (ADA2). The condition is also abbreviated as DADA2, which stands for deficiency of adenosine deaminase 2.
DADA2 is a relatively newly established condition. The patient suffers from inflammation of blood vessels or vasculitis, resulting in a condition called Polyarteritis nodosa is characterized by inflammation of small and medium-sized arteries. Symptoms depend on which blood vessels are affected.
ADA2 deficiency is a genetic disorder that is inherited in an autosomal recessive pattern. Individuals with the deficiency have a defect in the CECR1 gene, which is responsible for the production of ADA2 enzyme. The defect has to be present on both pairs of the chromosome for the disease to be apparent.
A defect in the gene could possibly affect inflammatory cells, resulting in excessive inflammation. The ADA2 enzyme could also possibly play an important role in maintaining the lining of blood vessels, a deficiency of the enzyme thereby affecting blood vessels.
Currently, there are very few cases diagnosed with the ADA2 deficiency. However, the gene defect as a cause of the vasculitis has been recognized only recently. Researchers feel that several patients with polyarteritis nodosa may also have the underlying gene defect. Genetic analysis of these individuals could detect many more cases of ADA2 deficiency that have gone unnoticed.
ADA2 deficiency may be detected in childhood where it may manifest as polyarteritis nodosa at an early age. Milder cases may develop symptoms only in adulthood. Symptoms depend on the organ affected as a consequence of vasculitis. Organs like the digestive tract, nervous tissue and kidneys are often affected. Symptoms and signs of ADA2 protein deficiency include the following:
- Fever, on and off
- Livedo reticulosa. It is a skin condition where the skin has a mottled, net-like appearance due to widening of small capillaries in the skin
- Joint pains
- Enlargement of lymph nodes
- Enlargement of the liver and spleen
- Repeated strokes
DADA2 can be suspected based on the history and physical examination of the patient. It may be suspected in a child with vasculitis, especially if there is another sibling with the same condition. Blood tests may detect inflammation and low levels of ADA2 enzyme. Definite confirmation of the condition is through genetic testing, in which the defective gene can be demonstrated.
Treatment of ADA2 protein deficiency is currently based on the symptoms and organ affected. However, anti-inflammatory drugs directed against the specific inflammatory reaction may produce a better effect. Etanercept has been tried out in a few cases with good result. Replacement of the absent enzyme or bone marrow transplant for the condition may be possible in the future. These treatment options however require further study.
Since ADA2 is a genetic problem, genetic counseling could be used to prevent its occurrence. The condition is inherited in an autosomal recessive pattern. This pattern requires that both the parents should have at least one defective gene to pass on the condition to their children. Thus, detection of the defective gene by genetic testing followed by proper counseling of the patient can help to prevent at least some cases of DADA2.
- Adenosine deaminase 2 deficiency - (http://ghr.nlm.nih.gov/condition/adenosine-deaminase-2-deficiency)
- NIH team discovers genetic disorder causing strokes and vascular inflammation in children - (https://www.genome.gov/27556385)
- Caorsi et al.: Long-term efficacy of etanercept in ADA2 deficiency. Pediatric Rheumatology 2014 12(Suppl 1):P72.
Latest Publications and Research on ADA2 Protein Deficiency
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