Abstract
Objectives: Identification of unusual renal pyrophosphate stone in 5 years old patient with congenital hypophosphatasia. Design: Case report and evaluation of laboratory results.
Settings: Department of Medical Chemistry and Clinical Biochemistry, University Hospital Motol, Charles University, Second Faculty of Medicine, Department of Paediatrics, University Hospital Motol, Charles University, Second Faculty of Medicine, V Úvalu 84, 150 06 Prague 5 (Czech Republic). Material and methods: Case report focusing on determination of urinary stone composition by polarized light microscopy and infra-red spectrometry.
Results: In 5 years old patient with effectively treated congenital hypophosphatasia by recombinant alkaline phosphatase (the serum value of which was ten times the upper limit of the reference range), rare pyrophosphate renal stone with addition of sulphate was demonstrated. The formation of the stone occurred in the period when the patient's urine was therapeutically alkalized (due to the history of urate stones) and the patient used prophylactically sulfonamides prior to planned lithotripsy.
Conclusion: Despite the high serum alkaline phosphatase concentration, the function of which is the conversion of pyrophosphate to phosphate, pyrophosphate renal stone was identified in a patient with congenital hypophosphatasia. The sulphate component of the stone is probably due to the prophylactic administration of sulfonamides.