A New Cause of Urinary Calculi: 2,8-Dihydroxyadenine Stones in Supposed ‘Uric Acid’ Crystalluria

Abstract

Most stones found in the human urinary tract are formed from common urinary constituents: calcium oxalate, calcium phosphate and ammonium magnesium phosphate. In situations of dehydration, aciduria or uric acid overproduction (as in gout, myeloproliferative disorders undergoing chemotherapy or deficiency of the enzyme HGPRTase in the Lesch-Nyhan syndrome), uric acid stones or gravel may form. In addition, overexcretion of normally minor urinary constituents, invariably compounds of limited solubility, may lead to stone formation, as in the renal tubular defect cystinuria, in xanthinuria, or in oroticacuria (1).We report the identification of 2,8-dihydroxyadenine, also a compound of limited solubility, as the principal constituent of recurrent stones in a young child (Fig 1) originally diagnosed as having uric acid crystalluria. This child is apparently homozygous for a deficiency of the enzyme adenine phosphoribosyl-transferase (APRTase).