Carbonic anhydrase II deficiency in three unrelated Japanese patients.

Three Japanese patients with carbonic anhydrase II (CAII) deficiency from three families were described. The parents of one patient were unrelated, the parents of each of the other two patients were first cousins. All the patients had renal tubular acidosis, osteopetrosis, symmetrical cerebral calcification and mental retardation. They exhibited poor activity and poor appetite in the neonatal period, and then developed psychomotor retardation. Two of them were diagnosed as having osteopetrosis at 10 months and 36 years of age, respectively, and the other as having osteomalacia at 28 years of age. All patients had recurrent episodes of muscle weakness. The CAII enzyme activity and protein levels in red blood cells in each of the three patients were deficient. Their parents exhibited approximately 50% normal levels of CAII activity and protein. This is the first report of patients with CAII deficiency in the Japanese population.