Reduced red blood cell carbonic anhydrase activity in a patient with nephrolithiasis

Low levels of red blood cell (RBC) carbonic anhydrase (CA) activity in hemoglobin-free hemolyzate (HFH) were found in 2 children with nephrolithiasis when compared to age-matched controls. The lowest levels were consistently found over a two year period in a 6 1/2 year old boy (U.P.) whose renal calculi contained uric acid, ammonia, calcium carbonate and oxalate. His RBC CA values ranged from 1.4-2.7 U/g Hb compared with levels of 3.9-5.3 U/g Hb in control subjects. Statistical comparisons of the mean values for U.P., 2.06 U/g Hb, and his age-matched control subjects, 4.46 U/g Hb, revealed a significant difference (P = less than 0.001). Similar reductions in RBC CA activity were found in his father--2.0 and 2.1 U/g Hb compared with 3.3 and 3.9 U/g Hb in adult controls. HFH CA activity was not decreased in the mother or sister. Polyacrylamide gel electrophoresis of HFH from 4 of the children and the father of U.P. was abnormal. However, this abnormal electrophoretic pattern could only be demonstrated when the gel was run for 120 minutes and not when it was run for 80 or 160 minutes. We have identified a patient and his father with low levels of RBC CA activity.