Adenine phosphoribosyltransferase deficiency is a rare autosomal recessive metabolic disorder caused by mutations of the APRT gene.

More commonly dihydroxyadenine nephropathy may develop insidiously, causing a progressive decline in kidney function over the span of several years.

[18] The adenine phosphoribosyltransferase (APRT) gene is found on chromosome 16q24, contains five exons, encompasses 2.8 kb of DNA, and has a coding region of 540 bp.

[20] All tissues express the APRT enzyme, which offers the sole metabolic route for recovering adenine from dietary and polyamine biosynthesis sources.

[6] Adenine phosphoribosyltransferase deficiency is diagnosed based on the identification of dihydroxyadenine by kidney stone analysis or examination of crystals in the urine.

[10] The combination of infrared spectroscopy and morphologic examination under a stereomicroscope allows for the identification of dihydroxyadenine in all cases of kidney stones and should be analyzed whenever one becomes available.

[26] Biochemical stone analysis is unreliable for diagnosing APRT deficiency and is unable to distinguish dihydroxyadenine from uric acid.

[10] For the identification of dihydroxyadenine crystals, light and polarizing microscopy examination of crystalluria is a very helpful, noninvasive, and reasonably priced method.