– Adenosine Desaminase (ADA) deficiency, is a purine metabolic disorder that cause severe combined immunodeficiency (SCID) due to the accumulation of toxic metabolites that primarily affects development, differentiation and function of T and B lymphocytes. Adenosine deaminase is a polymorphic enzyme that has an important role in immune functions and in the regulation of intracellular and extracellular concentrations of adenosine and adenosine receptor activity. ADA activity might be considered as a useful diagnostic tool among the other markers in these diseases. Genetic variability of ADA activity may have, therefore, an important role in resistance to malaria. Adenosine Deaminase (ADA) deficiency is an autosomal recessive variant of severe combined immunodeficiency (SCID) caused by systemic accumulation of ADA substrates.