Inheritance of adenine phosphoribosyltransferase (APRT) deficiency

Adenine phosphoribosyltransferase deficiency in Iceland

Two children and two adults of four unrelated families were on regular light microscopic examination found to exhibit identical, spherical urine crystals. Their characteristic appearance led to the diagnosis of 2,8-dihydroxyadenine crystalluria by spectrophotometric or gas-chromatographic/mass-spectrometric analysis. Total deficiency of adenine phosphoribosyltransferase was confirmed by direct measurements of the enzyme activity in lysed red blood cells. Close family members were also examined for the enzyme defect, revealing no additional homozygotes, but 13 heterozygotes among 14 relatives. We suggest that round, brownish urine crystals, even without radiolucent kidney stones, should alert the physician to search for the existence of 2,8-dihydroxyadenine. Proper treatment could then be instituted without delay, preventing eventual kidney damage.

Adenine phosphoribosyltransferase deficiency: 2,8-dihydroxyadenine urolithiasis in a 48-year-old woman

We report the first patient in Finland and Scandinavia with a deficiency of adenine phosphoribosyltransferase (APRT). About 30 clinically affected patients have been reported in the literature. APRT deficiency is an enzyme disorder which is inherited autosomally in a recessive manner. The use of adenine in purine metabolism is disturbed and it accumulates in the body, where it is oxidised to poorly insoluble 2,8-dihydroxyadenine by xanthine oxidase. The dihydroxyadenine forms stones which can be mistaken for uric acid stones. Our patient had had frequent episodes of urolithiasis and the diagnosis was finally made after pyelolithotomy and stone analysis. The total APRT deficiency was detected in the haemolysate of erythrocytes. Partial deficiency of APRT in the patient's relatives showed heterozygosity of the enzyme defect. The only clinical manifestation of the defect is the formation of urinary stones. This can be prevented by diet and allopurinol.

2,8-dihydroxyadenine urolithiasis: review of the literature and report of a case in the United States

Urolithiasis resulting from inherited metabolic derangement is rare. Only 13 cases of 2,8-dihydroxyadenine stones resulting from a deficiency of the enzyme adenine phosphoribosyl transferase have been reported since 1974. Of these cases 9 have been in children with the homozygous trait. To date, 3 homozygous and 1 heterozygous adults with urolithiasis have been reported. This disease has not been associated with any other clinical or biochemical abnormalities. Treatment includes low purine diet and allopurinol. We herein report a case of complete adenine phosphoribosyl transferase deficiency associated with 2,8-dihydroxyadenine urolithiasis in the United States, bringing the total to 14 in the literature.