Carbonic anhydrase and fetal hemoglobin in tyrotoxicosis.

I N A RECENT REPORT Lie-Injo and 1 described a condition char.. acterized by a deficiency of both types I and 112 (also designated B and C) of carbonic anhydrase. This deficiency, though associated with a high level of fetal hemoglobin, was not due to hemoglobinopathy, hereditary persistence of fetal hemoglobin, or any of the known types of thalassemia. Because of lack of proof of hereditary basis and uncertainty whether the changes in the patient were caused by a specific etiology, the condition was designated as a new syndrome rather than as a specific disease entity, as such a combination of findings had not been described before. These findings prompted us to study erythrocyte carbonic anhydrase levels in different disease states, especially those with unexplained increase of fetal hemoglobin. \Ve now report the occurrence of carbonic anhydrase deficiency in patients with thyrotoxicosis, several of whom had an increase of HbF level in the blood.