Purine metabolism and immunodeficiency: urinary purine excretion as a diagnostic screening test in adenosine deaminase and purine nucleoside phosphorylase deficiency.

1. We have compared urinary purine excretion by two different methods in three separate paediatric disorders of purine metabolism: purine nucleo­ side phosphoryiase deficiency, adenosine deaminase deficiency and adenine phosphoribosyltransferase deficiency. 2. The abnormal purines identified in each case were specific for the defect and directly related to it: adenine in adenine phophoribosyltransferase deficiency; the abnormal nucleosides inosine, guanosine and their corresponding deoxyribosides in purine nucleoside phosphoryiase deficiency; deoxyadenosine in adenosine deaminase deficiency, the latter having previously been identified erron­ eously as adenine after degradation in the acidic conditions used. 3. Deoxyriboside excretion was specific for the two defects associated with immunodeficiency; adenine for adenine phosphoribosyltransferase deficiency and 2,8-dihydroxyadenine urolithiasis. The results obtained by a quantitative method were reflected in a simple rapid qualitative technique, isotachophoresis of the urine. 4. Purine overexcretion (principally inosine) was evident only in purine nucleoside phosphoryiase deficiency, which emphasizes the importance of hypoxanthine salvage for the overall control of purine production in man. In none of these dis-