APRT and Nephropathy: Adenine phosphoribosyltransferase (APRT) deficiency is a rare autosomal recessive inherited disorder of purine metabolism that usually manifests as 2,8-dihydroxyadenine (DHA) nephropathy due to excessive DHA crystal deposition in the tubular lumen and interstitium of the kidney, leading to inflammation and severely impaired renal function22.