Abstract
Adenine phosphoribosyltransferase (APRT) deficiency results in 2,8-dihydroxyadenine (DHA) urolithiasis with the deposition of 2,8-DHA crystals of various sizes in the bladder. Here, we report the case of a male patient in his 60s, who was diagnosed as having diabetes in 2012, and regularly came to our hospital for the treatment of chronic renal failure caused by diabetic nephropathy. Crystals suspected to be composed of 2,8-DHA were first detected about 2 years later and were consistently detected thereafter. Inspection of their chemical properties suggested that these crystals were composed of 2,8-DHA. However, the final determination was difficult as they could not be identified by infrared spectroscopic analysis, and computed tomography did not show any urinary calculus. Genetic analysis showed the patient to be homozygous for the Japanese mutant gene APRT*J/APRT*J. The timing of the first detection of 2,8-DHA coincided with that of eGFR deterioration. Therefore, the possibility that 2,8-DHA crystals were the cause of the reduced renal function was suggested. As experiments in rats confirmed that 2,8-DHA crystals cause kidney toxicity, even in the absence of calculus, the patient was started on medication for hyperuricemia, which also controls 2,8-DHA biosynthesis. In this case, the diagnosis was made and treatment commenced on the basis of a report from a clinical laboratory regarding the crystals, and is an example whereby analysis of urinary sediment contributed to clinical management.
