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Abstract: TH-PO843

Adenine Phosphoribosyl Transferase Deficiency Caused Obstructive Nephropathy: A Case Report

Session Information

Category: Health Maintenance‚ Nutrition‚ and Metabolism

  • 1400 Health Maintenance‚ Nutrition‚ and Metabolism


  • Sung, Jonathan, Harbor-UCLA Medical Center, Torrance, California, United States
  • Tong, Lili, Harbor-UCLA Medical Center, Torrance, California, United States
  • Dai, Tiane, Harbor-UCLA Medical Center, Torrance, California, United States

Adenine phosphoribosyl transferase deficiency (APRTD) is a rare autosomal recessive metabolic disorder. It causes excessive production and renal excretion of 2,8 dihydroxyadenine (DHA), which leads to nephrolithiasis. Characterized by radiolucency, which is similar to uric acid stones, they are often misdiagnosed or missed, which can often lead to progressive renal failure, even in transplanted patients. We report a case of APRTD in a woman with an incidental finding of unilateral hydroureteronephrosis from ureteral stone.

Case Description

A 57 year-old Mexican female, with known medical history of hypertension and extensive peripheral arterial disease requiring multiple interventions including aortobifemoral bypasses, was referred to urology for incidentally noted persistent right-sided severe hydroureteronephrosis from an obstructive right mid ureteral stone. Patient underwent ureteroscopy with stone extraction and laser lithotripsy of the right ureteral stone. Stone analysis revealed a 2,8-dihydroxyadenine stone. She was subsequently referred to nephrology for management and Human Genetics for genetic testing/counseling. Patient was asymptomatic. Patient was started on allopurinol 300mg daily, which inhibits xanthine oxidoreductase and results in adenine urinary excretion instead of 2,8-dihydroxyadenine, and hydration. She has continued to have relatively stable renal function without known recurrence of nephrolithiasis. She had APRT gene sequencing, and the results revealed homozygous pathogenic variant in APRT gene, c.294G>A (p. Trp98Ter).


APRTD is characterized by a mutation on chromosome 16q24, affecting the gene for adenine phosphoribosyltransferase resulting in accumulation of the insoluble purine 2,8-dihydroxyadenine in the kidneys. This can result in crystalluria and nephrolithiasis, which can lead to hydronephrosis and chronic, progressive renal disease. Generally, two different types of mutations have been described. Type I APRT deficiency has virtually absent enzyme activity whereas Type II deficiency has functionally decreased activity. 2, 8-dihydroxyadenine stones are similar to uric stones as they are both radiolucent and have identical chemical reactivity. The treatment is allopurinol and hydration. Stone retrieval and stone analysis play pivotal roles in the diagnosis of APRTD induced nephrolithiasis and guide further management.