Transfusion of carbonic anhydrase‐replete erythrocytes fails to correct the acidification defect in the syndrome of osteopetrosis, renal tubular acidosis, and cerebral calcification (Carbonic Anhydrase‐II Deficiency)

We explored the effects of transfusion of carbonic anhydrase II (CA‐II)‐replete erythrocytes on systemic pH, serum electrolytes, and urinary acidification of a patient with CA‐II deficiency. Pretransfusion studies documented hyperchloremic acidosis, increased urinary pH with decreased titratable acidity, and profound CA‐II deficiency in erythrocytes. During transfusion, CA‐II in circulating erythrocytes increased to above the half‐normal levels seen in asymptomatic heterozygote carriers of CA‐II deficiency. However, no significant change occurred in venous, arterial or urinary pH, serum electrolytes, and urinary acid excretion during the transfusion or during the subsequent 60 hr of observation. These studies argue that the renal acidification defect in CA‐II deficiency results from deficiency of CA‐II in the renal parenchyma, and is not secondary to deficiency of CA‐II in erythrocytes. Bone marrow transplantation is not a promising approach to correct the renal manifestations of CA‐II deficiency.