Adenosine deaminase deficiency is seen in the following:
Common variable immunodeficiency
Severe combined immunodeficiency
Chronic granulomatous disease
Nezelof syndrome
The most common cause of autosomal recessive severe combined immunodeficiency(SCID) is the deficiency of enzyme adenosine deaminase (ADA)Defect lies in lymphoid stem cells, resulting in failure of both T and B cellsDeficiency of ADA leads to accumulation of deoxyadenosine & its derivatives, which are toxic to immature lymphocytes, especially those of T lineage, and this may account for the marked decrease in T lymphocyte number in severe cases(ref: Harrison's 18/e p2700)
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