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PubMed This is a summary of 41 peer-reviewed journal articles Updated
Nephrology

Understanding APRT Deficiency: From Uncertainty to Clarity

At a Glance

APRT deficiency is a rare genetic disorder that causes 2,8-DHA crystals to form in the kidneys, leading to recurrent stones and potential damage. Though frequently misdiagnosed as common uric acid stones, it is highly treatable with daily medication to stop crystal formation and protect kidney health.

If you are reading this, you may have spent years searching for answers to recurring kidney stones or unexplained kidney issues. Finding out that you or your child has adenine phosphoribosyltransferase (APRT) deficiency can be overwhelming, but it is also a significant turning point. While this condition is rare and serious if left untreated, it is one of the most treatable causes of kidney damage [1][2].

What is APRT Deficiency?

APRT deficiency is a rare metabolic disorder, which means the body has trouble processing certain natural substances [1]. Although the damage happens in the kidneys, it is not a primary kidney disease. Instead, the body lacks a specific enzyme (a protein that triggers chemical reactions) called APRT [3].

Without this enzyme, a substance called adenine builds up and is converted into 2,8-dihydroxyadenine (2,8-DHA) [1][4]. This 2,8-DHA is very hard for the body to dissolve. It forms sharp, needle-like crystals in the urine that can clump together into stones or get stuck directly inside the kidney tissue, causing inflammation and scarring [5][6].

Understanding the Rarity and Genetics

APRT deficiency is an autosomal recessive condition [7]. This means a person must inherit two changed genes—one from each parent—to have the disorder. It is estimated to affect between 1 in 50,000 to 1 in 100,000 people worldwide [7].

Because it is so rare, many doctors may never see a case in their entire career. However, it is more common in certain areas due to founder effects (where a specific genetic trait becomes more common in a population that started from a small group of ancestors), particularly in Japan and Iceland [7][8].

The Challenge of Getting a Name

It is common for patients with APRT deficiency to face a delayed diagnosis, sometimes waiting years or decades while being treated for more common types of kidney stones [9][10].

  • The “Uric Acid” Trap: 2,8-DHA crystals look very similar to uric acid crystals under a standard microscope. Many laboratories mistakenly report them as uric acid, leading to incorrect treatments [5][11].
  • Stone Analysis Hurdles: Standard automated stone analysis often fails to identify 2,8-DHA [8][11]. Precise identification usually requires specialized tests like infrared spectroscopy or X-ray diffraction performed by experts [5][12].

While a late diagnosis can be frustrating and frightening, especially if kidney function has declined, having the correct diagnosis now means you can finally start the right treatment to stop further damage [13][2].

A Highly Treatable Diagnosis

The most important thing to know is that APRT deficiency is highly treatable. Once the diagnosis is confirmed, the goal is simple: stop the crystals from forming [1].

  1. Medication: Daily use of medications called xanthine dehydrogenase inhibitors—such as allopurinol or febuxostat—blocks the enzyme that creates the harmful 2,8-DHA [1][14].
  2. Stopping the Damage: These medications can drastically reduce or even eliminate new crystal formation [1][15]. For many patients, this prevents new stones and stops the progression of kidney disease [13][1].
  3. Preserving Kidney Health: Even for those who already have significant kidney damage or have had a kidney transplant, starting this treatment is critical to protecting the kidney function they have left [13][16].

By identifying this condition, you have moved from a place of “unexplained” damage to a place of “manageable” health. With consistent treatment and monitoring, the outlook for most patients is excellent [2][17].

For more details on navigating this condition, please read:

01

The Biology of APRT Deficiency and Avoiding the Diagnostic Trap

Learn the biology of APRT deficiency and how 2,8-DHA crystals form. Understand why these stones mimic uric acid, the genetics, and how to avoid misdiagnosis.

02

Confirming the Diagnosis: Understanding Your Tests

Learn how APRT deficiency is diagnosed. Understand key tests including specialized kidney stone analysis, fresh urine microscopy, and APRT genetic testing.

03

Standard of Care: Medications and Daily Management

Learn about standard treatments for APRT deficiency, including allopurinol and febuxostat. Understand dosing, lifelong adherence, and daily fluid needs.

04

Protecting Your Kidneys Long-Term: Survivorship and Monitoring

Learn how to manage APRT deficiency long-term to protect your kidneys. Discover the importance of urine microscopy, transplant safety, and XOR inhibitors.

Common questions in this guide

What is APRT deficiency?
APRT deficiency is a rare genetic metabolic disorder where the body lacks a specific enzyme. This causes a substance called 2,8-DHA to build up and form sharp crystals in the urine, which can lead to recurrent kidney stones and kidney tissue damage.
Why is APRT deficiency frequently misdiagnosed?
The 2,8-DHA crystals caused by this condition look almost identical to uric acid crystals under a standard microscope. Routine laboratory tests often mistake them for uric acid, which can lead to years of incorrect treatments and delayed diagnosis.
How is APRT deficiency treated?
It is highly treatable using daily medications called xanthine dehydrogenase inhibitors, such as allopurinol or febuxostat. These medications block the production of harmful 2,8-DHA crystals, which prevents new stones from forming and protects remaining kidney function.
Should my family members be tested for APRT deficiency?
Yes. Because APRT deficiency is an autosomal recessive genetic condition, your siblings and other close family members may also have it. Testing family members is highly recommended even if they do not currently have symptoms, as early treatment can prevent severe kidney damage.
How can I confirm my kidney stones are caused by APRT deficiency?
Specialized testing is required to accurately identify 2,8-DHA stones. Your doctor can use advanced methods like infrared spectroscopy, X-ray diffraction, or perform a fresh urine sediment test under polarized light to look for the specific crystals.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.If my stones were previously identified as uric acid, what specific tests can be done to re-verify if they are actually 2,8-DHA?
  2. 2.What is my current level of kidney function, and do you see signs of existing crystal damage (crystalline nephropathy)?
  3. 3.Can we perform a 'fresh' urine sediment test under polarized light to look for 2,8-DHA crystals?
  4. 4.Given this is a genetic condition, should my siblings or other family members be tested even if they have no symptoms?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (17)
  1. 1

    A rare cause of urolithiasis in an infant: Answers.

    Koyun M, Sancaktar M, Aksoy GK, et al.

    Pediatric nephrology (Berlin, Germany) 2021; (36(7)):2067-2068 doi:10.1007/s00467-020-04910-y.

    PMID: 33459934
  2. 2

    Kidney Disease in Adenine Phosphoribosyltransferase Deficiency.

    Runolfsdottir HL, Palsson R, Agustsdottir IM, et al.

    American journal of kidney diseases : the official journal of the National Kidney Foundation 2016; (67(3)):431-8.

    PMID: 26724837
  3. 3

    Genetic defects underlying renal stone disease.

    Rumsby G

    International journal of surgery (London, England) 2016; (36(Pt D)):590-595 doi:10.1016/j.ijsu.2016.11.015.

    PMID: 27838384
  4. 4

    Germ-Free Conditions Modulate Host Purine Metabolism, Exacerbating Adenine-Induced Kidney Damage.

    Mishima E, Ichijo M, Kawabe T, et al.

    Toxins 2020; (12(9)) doi:10.3390/toxins12090547.

    PMID: 32859011
  5. 5

    A virtuous diagnostic and therapeutic roadmap triggered by a motivated and skilful urinary sediment examination.

    Garigali G, Marra G, Rizzo V, et al.

    Clinica chimica acta; international journal of clinical chemistry 2019; (492()):23-25 doi:10.1016/j.cca.2019.01.026.

    PMID: 30707895
  6. 6

    Cellular and Molecular Mechanisms of Kidney Injury in 2,8-Dihydroxyadenine Nephropathy.

    Klinkhammer BM, Djudjaj S, Kunter U, et al.

    Journal of the American Society of Nephrology : JASN 2020; (31(4)):799-816 doi:10.1681/ASN.2019080827.

    PMID: 32086278
  7. 7

    Allele frequency of variants reported to cause adenine phosphoribosyltransferase deficiency.

    Runolfsdottir HL, Sayer JA, Indridason OS, et al.

    European journal of human genetics : EJHG 2021; (29(7)):1061-1070 doi:10.1038/s41431-020-00805-6.

    PMID: 33707627
  8. 8

    Adenine Phosphoribosyltransferase Deficiency: A Rare Cause of Recurrent Urolithiasis.

    Jaffer A, Joyce A, Koenig P, Biyani CS

    Journal of endourology case reports 2017; (3(1)):49-51 doi:10.1089/cren.2017.0015.

    PMID: 28466077
  9. 9

    Kidney stone analysis may miss diagnoses as demonstrated by a case of adenine phosphoribosyl transferase deficiency.

    Bramley R, Herrera D, Barski R, Henderson M

    Annals of clinical biochemistry 2026; (63(2)):177-180 doi:10.1177/00045632251367232.

    PMID: 40810356
  10. 10

    2,8-Dihydroxyadenine Nephropathy Identified as Cause of End-Stage Renal Disease After Renal Transplant.

    George SA, Al-Rushaidan S, Francis I, et al.

    Experimental and clinical transplantation : official journal of the Middle East Society for Organ Transplantation 2017; (15(5)):574-577 doi:10.6002/ect.2015.0096.

    PMID: 27447713
  11. 11

    Are conventional stone analysis techniques reliable for the identification of 2,8-dihydroxyadenine kidney stones? A case series.

    Runolfsdottir HL, Lin TL, Goldfarb DS, et al.

    Urolithiasis 2020; (48(4)):337-344 doi:10.1007/s00240-020-01187-6.

    PMID: 32399606
  12. 12

    A case of 2,8-DHA crystalline nephropathy caused by adenine phosphoribosyltransferase deficiency: diagnosis and treatment.

    Kunou M, Yamaguchi M, Takahashi H, et al.

    CEN case reports 2023; (12(3)):329-334 doi:10.1007/s13730-022-00768-1.

    PMID: 36576711
  13. 13

    Long-term renal outcomes of APRT deficiency presenting in childhood.

    Runolfsdottir HL, Palsson R, Agustsdottir IM, et al.

    Pediatric nephrology (Berlin, Germany) 2019; (34(3)):435-442 doi:10.1007/s00467-018-4109-x.

    PMID: 30443743
  14. 14

    Comparison of the effect of allopurinol and febuxostat on urinary 2,8-dihydroxyadenine excretion in patients with Adenine phosphoribosyltransferase deficiency (APRTd): A clinical trial.

    Edvardsson VO, Runolfsdottir HL, Thorsteinsdottir UA, et al.

    European journal of internal medicine 2018; (48()):75-79 doi:10.1016/j.ejim.2017.10.007.

    PMID: 29241594
  15. 15

    2,8-dihyroxyadenine (DHA) crystalline nephropathy: A case report.

    Rather JI, Fatima M, Wani MM, et al.

    Clinical nephrology. Case studies 2025; (13()):37-40 doi:10.5414/CNCS111590.

    PMID: 40182129
  16. 16

    Kidney Transplant Outcomes in Patients With Adenine Phosphoribosyltransferase Deficiency.

    Runolfsdottir HL, Palsson R, Agustsdottir IMS, et al.

    Transplantation 2020; (104(10)):2120-2128 doi:10.1097/TP.0000000000003088.

    PMID: 31880754
  17. 17

    [A Case Report of 2,8-Dihydroxyadenine Stone].

    Yamaguchi S, Haba T, Koike H

    Hinyokika kiyo. Acta urologica Japonica 2015; (61(7)):279-83.

    PMID: 26278213

This page provides educational information about APRT deficiency and kidney health. It is not a substitute for professional medical advice, so always consult a nephrologist or healthcare provider for proper diagnosis and treatment.

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