Adenine phosphoribosyltransferase deficiency

Adenine phosphoribosyltransferase deficiency
Dihydroxyadenine.png
Dihydroxyadenine, an insoluble purine
Synonyms	APRT deficiency, 2,8-Dihydroxyadenine urolithiasis
Specialty	Nephrology, Genetics
Symptoms	Hematuria, kidney stones, flank pain, urinary tract obstruction
Complications	Chronic kidney disease, nephrolithiasis, renal failure
Usual onset	Childhood or early adulthood
Duration	Lifelong
Types	Type I (complete enzyme deficiency), Type II (residual activity)
Causes	Mutation in the APRT gene (autosomal recessive)
Risk factors	Family history, consanguinity
Diagnosis	Stone analysis, urinary dihydroxyadenine crystals, genetic testing, enzyme assay
Differential diagnosis	Uric acid stones, xanthinuria, cystinuria
Prevention	Early diagnosis and treatment
Treatment	High fluid intake, low purine diet, urine alkalinization
Medication	Allopurinol, febuxostat
Prognosis	Good with early diagnosis and lifelong treatment
Frequency	Rare (estimated <1:100,000 worldwide)
Deaths	Rare; related to renal complications if untreated

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Adenine phosphoribosyltransferase deficiency has an autosomal recessive pattern of inheritance.

Adenine phosphoribosyltransferase deficiency (APRT deficiency) is a rare autosomal recessive disorder that affects the body's ability to process adenine, a component of nucleic acids. This metabolic disorder leads to the accumulation of 2,8-dihydroxyadenine (DHA) in the urine, which can cause kidney stones and renal failure.

Pathophysiology

APRT deficiency is caused by mutations in the APRT gene, which encodes the enzyme adenine phosphoribosyltransferase. This enzyme is responsible for the conversion of adenine to adenosine monophosphate (AMP) in the purine salvage pathway. When APRT is deficient or non-functional, adenine is instead converted to 2,8-dihydroxyadenine, a poorly soluble compound that precipitates in the urinary tract, leading to stone formation and potential kidney damage.

Clinical Presentation

Patients with APRT deficiency may present with symptoms related to kidney stones, such as hematuria, flank pain, and urinary tract infections. In severe cases, chronic kidney disease or acute renal failure may occur due to the accumulation of DHA crystals in the renal tubules.

Diagnosis

The diagnosis of APRT deficiency is typically confirmed through genetic testing to identify mutations in the APRT gene. Additionally, the presence of DHA crystals in the urine can be detected using specialized microscopy techniques. Urinary DHA levels can also be measured to support the diagnosis.

Treatment

Management of APRT deficiency involves reducing the production of DHA and preventing stone formation. This can be achieved through dietary modifications, such as reducing purine intake, and the use of medications like allopurinol or febuxostat, which inhibit xanthine oxidase and decrease the production of DHA. Adequate hydration is also crucial to prevent stone formation.

Prognosis

With appropriate treatment and management, individuals with APRT deficiency can lead normal lives. However, if left untreated, the condition can lead to significant renal damage and complications.

Related Pages

• Purine metabolism disorders
• Kidney stone disease
• Genetic disorders

External links

• Adenine phosphoribosyltransferase deficiency at NIH's Office of Rare Diseases