He however had normal plasma and urine oxalate and the genotype screen for primary hyperoxaluria was negative. Urine crystal analysis revealed typical maltese cross crystals and APRT deficiency was subsequently confirmed through red cell and enzymatic analysis. He was commenced on Allopurinol and Feboxustat and eventually managed to hold off dialysis after 17 months of dialysis post-transplant. This evidence concerns the gene APRT and hyperinsulinemic hypoglycemia, familial, 4.