Adenine phosphoribosyltransferase deficiency, which is also known as APRTD or APRT deficiency, is a rare inherited inborn error of metabolism (IEM) leading to the recurrent formation of kidney stones. It is an autosomal recessive disorder associated with a mutation in the enzyme adenine phosphoribosyltransferase (APRT). APRT is involved in the nucleotide salvage pathway, which provides an alternative, and energetically more efficient route to nucleotide biosynthesis in humans and most other animals. A defect in this enzyme can lead to the accumulation of the insoluble purine known as 2,8-dihydroxyadenine. In particular, when APRT has reduced or nonexistent activity, adenine accumulates which is then degraded by xanthine dehydrogenase to 2,8-dihydroxyadenine (DHA). 2,8-Dihydroxyadenine is a derivative of adenine which accumulates in 2,8 dihydroxyadenine urolithiasis (kidney stones). Kidney and urinary tract stones can obstruct the urinary tract, resulting in pain and difficulty urinating. If left untreated, the condition can eventually produce kidney failure. APRTD was first diagnosed in 1976. There are two categories of APRTD: type I involves a complete loss of the APRT function while type II involves a partial loss and is mostly found in Japan. APRT deficiency is estimated to affect 1 in 27 000 people in Japan. APRTD is rarer in Europe, where it affects 1 in 50 000 to 100 000 people. A diagnosis of APRTD can be made by analyzing kidney stones or measuring DHA concentrations in urine. APRTD is treatable with regular doses of allopurinol, which inhibits xanthine dehydrogenase activity. APRTD can also be treated with a low-purine diet and a high fluid intake.

Adenine Phosphoribosyltransferase Deficiency (APRT) References

Purine Metabolism References