Adenosine deaminase (ADA) deficiency is an autosomal recessive disorder, a type of SCID (severe combined immune deficiency) in which immune system is affected. It occurs because of the mutation in chromosome 20 which leads to deficiency of enzyme adenosine deaminase. it causes accumulation of deoxyadenosine (or dATP) which inhibits DNA synthesis, so cells are unable to divide. High level of dATP produces a general deficiency of T Lymphocytes however the basis of B Lymphocytes toxicity is less clear.
