Renal tubular acidosis, osteopetrosis, and cerebral calcification – The triad of carbonic anhydrase II deficiency

A 43-year-old Omani lady was admitted with acute-onset mild weakness of all four limbs. She had a history of developmental delay and multiple fractures in the past. She had dysmorphic facies (prominent forehead, micrognathia, and misaligned teeth), low intelligence quotient (48), and grade 4/5 power in all 4 limbs. Biochemical parameters showed renal tubular acidosis (RTA). She also had osteopetrosis and cerebral calcification on evaluation. Carbonic anhydrase II deficiency (CAII deficiency) was diagnosed based on the presence of osteopetrosis, RTA, and cerebral calcification. She was managed with intravenous potassium chloride and was discharged on oral potassium chloride with sodium bicarbonate supplementation. The case highlights the importance of considering CAII deficiency in patients presenting with RTA with other features such as osteopetrosis and cerebral calcification.