title: An unusual patient with kidney stones composed of 1-methyluric acid.
abstract: An unusual case with kidney stones composed mainly of 1-methyluric acid is described. The patient, a Caucasian male of Celtic descent, reportedly drank at least eight cups of coffee per day and had a long history of rheumatoid arthritis, gouty attacks and renal colics--the latter attributed to nephrocalcinosis and analgesic nephropathy. He was treated with allopurinol. At 54 years, a bilateral nephrolithotomy was performed. Stone samples were analysed by thermogravimetry and infrared spectroscopy and reported to be 12-25% calcium oxalate, the remainder being organic uric acid-like material. Analysis of the extracts by HPLC confirmed that the organic material contained 67% of 1-methyluric acid and 33% of uric acid. Possible mechanisms leading to the precipitation of 1-methyluric acid from urine are discussed. We conclude that the high caffeine intake resulted in extremely elevated urinary concentrations of 1-methyluric acid favouring the formation of 1-methyluric acid stones.
authors.affiliation: Purine Research Unit, 5th Floor Thomas Guy House, Guy's Hospital, SE1 9RT, London Bridge, UK.
authors.forename: Phillip M
authors.initials: PM
authors.lastname: Davies
authors.forename: Lynette D
authors.initials: LD
authors.lastname: Fairbanks
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Safranow
authors.forename: Michael R
authors.initials: MR
authors.lastname: Bending
authors.forename: H Anne
authors.initials: HA
authors.lastname: Simmonds
mesh_terms: D000328:Adult; D002110:Caffeine / Q000493:pharmacokinetics; D000697:Central Nervous System Stimulants / Q000493:pharmacokinetics; D003069:Coffee; D006801:Humans; D007669:Kidney Calculi / Q000150:complications* / Q000652:urine*; D007676:Kidney Failure, Chronic / Q000209:etiology* / Q000628:therapy; D008297:Male; D010531:Peritoneal Dialysis, Continuous Ambulatory; D014527:Uric Acid / Q000031:analogs & derivatives* / Q000378:metabolism / Q000652:urine
chemical_list: D000697:Central Nervous System Stimulants; D003069:Coffee; D014527:Uric Acid; C030530:1-methyluric acid; D002110:Caffeine