Stone-forming conditions such as cystinuria [24], primary hyperoxaluria [13] and adenine phosphoribosyltransferase (APRT) deficiency (producing 2,8-dihydroxyadenine stones) [26] are all also associated with risk of progression to end-stage renal disease, highlighting the crucial need for prompt diagnosis and preventative measures. Here, APRT is linked to hyperinsulinemic hypoglycemia, familial, 4.