This test is to look for a rare metabolic disease, adenosine deaminase 2 deficiency (ADA2). There are two forms of the ADA enzyme, ADA1 and ADA2. ADA1 is encoded by the ADA gene and is found in all cells. A deficiency of this enzyme results in severe combined immunodeficiency. ADA2 is encoded by the CECR1 gene and the enzyme is found in extracellular liquid (plasma).
Polyarteritis nodosa vasculopathy and early onset stroke and vasculopathy are the main presenting symptoms, but myalgia/arthralgia, liver racemosa, hepatosplenomegaly, erthyema nodosum, eye problems, gastrointestinal problems, antibody deficiency and immune dysregulation, pure red cell aplasia, haemolytic anaemia have also been associated with ADA2 deficiency.