Two birds one stone-two rare cases of adenine phosphoribosyl transferase deficiency

Complete adenine phosphoribosyl transferase (APRT) deficiency is a rare inherited metabolic disorder that leads to the formation and hyperexcretion of 2,8-dihydroxyadenine (DHA) into urine. We had a 52-year-old male with Hypertension for 18 months, presented for routine evaluation and was found to have creatinine of 4.29 mg/dl. His urine analysis was done which showed no proteinuria or urinary sediments. His USG done demonstrated normal sized kidneys with mildly increased echogenicities. He underwent a renal Biopsy for etiology determination. Similarly, we had another case of a 54-year-old female with no comorbidities who was identified to have chronic kidney disease in 2018 with a baseline creatinine of 2 mg/dl came with uremic symptoms and history of NSAID intake in June 2019. Her creatinine peaked to 7.9 mg/dl. Urine analysis displayed 1+ proteinuria with no active sediments. Her USG of the kidneys showed normal kidneys with increased echogenicities. She underwent renal biopsy for etiology determination. Biopsy of case 1 showed chronic interstitial nephritis and case 2 showed acute interstitial nephritis. Both biopsies showed deposition of 2,8-dihydroxyadenine crystals. Genetic analysis of both cases showed an exon mutation in chromosome 16