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1079 REDUCED CONCENTRATION OF RED BLOOD CELL(RBC) CARBONIC ANHYDRASE(CA) IN A PATIENT WITH NEPHROLITHIASIS

No underlying cause can be found to account for stone formation in about 1/3 of children with nephrolithiasis.We have found a reduction in total RBC CA activity(measured by the nonspecific esterolytic activity of CA on para-nitrophenyl acetate) in a 6½ yr old boy with idiopathic nephrolithiasis.Over a 2 yr period his CA concentrations(n=5)were 1.4-2.7 units/g Hb(mean=2.06). Age-matched controls measured at the same time(n=5)had values of 3.9-5.3(mean=4.46)units/g Hb(p= < 0.001).CA concentrations of 5 other boys with calculi were(n=8)4.35 compared to 4.58 units/g Hb in controls(p= > 0.1).CA activity of the proband's father's RBC was also reduced(n= 2):2.05 units/g Hb compared with 3.6 units/g Hb in controls.However the concentrations of RBC CA activity in the mother and sister were normal.Polyacrylamide gel electrophoresis of HFH was abnormal in patient and father but not in mother and sister.Neither B nor C peaks could be demonstrated from proband and father.Although urine acidification appeared to be normal in the patient,he did not have normal postprandial alkaline tides.We thus appear to have identified a patient in whom reduced RBC CA activity may be associated with a propensity to stone formation.