Which clinical history findings are characteristic of adenosine deaminase (ADA) deficiency?

Updated: Aug 11, 2020
  • Author: Francisco J Hernandez-Ilizaliturri, MD; Chief Editor: Emmanuel C Besa, MD  more...
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ADA is an enzyme of the purine salvage pathway. Deficiency leads to the accumulation of dATP and 2'-deoxyadenosine. dATP is lymphocytotoxic because of its ability to inhibit DNA synthesis via inhibition of ribonucleotide reductase. The nucleoside 2'-deoxyadenosine inhibits the enzyme S-adenosyl-L-homocysteine (SAH) hydrolase, which results in accumulation of SAH, a potent inhibitor of all cellular methylation reactions. Both B and T cells are affected. The phenotype is T–B–NK–.

ADA deficiency is an autosomal recessive disorder in which the age at presentation varies. Failure of the immune system is progressive and may not fully manifest in certain individuals until adulthood.

This disease has the same symptoms of XSCID, that is, recurrent infections, persistent opportunistic infections, and GVHD susceptibility. Clinically, ADA deficiency differs from XSCID by (1) the presence of skeletal and chest wall abnormalities involving the vertebral bodies and the chondrocostal junctions and (2) the possible presence of thymic differentiation with rare Hassall concentric corpuscles.

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