APRT and hyperinsulinemic hypoglycemia, familial, 4: A high index of suspicion is required to diagnose APRT deficiency, and there should be a low threshold to consider this possibility, especially in patients presenting with urinary stones and renal impairment, early-onset urinary stones, frequent recurrence of stones, and unexplained renal failure. Early diagnosis and prompt initiation of therapy are key in retarding the progression of the disease.