Adenine Phosphoribosyltransferase Deficiency : a potentially reversible cause of CKD

Adenine phosphoribosyltransferase (APRT) enzyme deficiency is an important and potentially reversible cause of progressive chronic kidney disease. It is a rare, autosomal recessive disorder that was first described in 19741 with more than 40 known mutations2, 3 and estimated prevalence of 1 in 50,000 to 100,000 persons.2, 4, 5 The APRT enzyme is important for the conversion of adenine to adenosine monophosphate in the salvage purine pathway. Deficiency of this enzyme results in the metabolism of adenine into 2,8-dihydroxyadenine (DHA) by xanthine oxidase (xanthine dehydrogenase) (Figure 1a). DHA is highly insoluble in urine and will precipitate to cause either urolithiasis or crystal nephropathy. There are no known extrarenal manifestations and reasons for this remains unclear given the extensive tissue distribution of this enzyme.