Crystalline Nephropathy due to APRT Deficiency: A Preventable Cause of Renal and Renal Allograft Failure

Adenine phosphororibosyl transferase (APRT) deficiency, a rare inborn error of metabolism is inherited as an autosomal recessive trait. It presents with 2,8-dihydroxyadenine (2,8-DHA) crystal nephropathy and recurrent nephrolithiasis and often progresses to end stage renal disease (ESRD). After transplant, it can recur in the allograft. If APRT deficiency is recognized early, renal failure can be prevented, arrested or reversed in native kidney and in allograft by treatment with allopurinol, which inhibits xanthine oxidase and reduces 2,8-DHA formation. We report two cases of APRT deficiency from our center. DNA sequencing of APRT gene performed in one of the cases revealed a pathogenic variant in Exon1 of APRT gene (c.3G>C; p.Met1). This variant affects the translation initiation codon and results in a start loss. The variant has previously been reported in two cases with APRT deficiency.