Blessing in disguise: when head trauma solves the riddle of carbonic anhydrase II deficiency.

Carbonic anhydrase II deficiency is a rare autosomal recessive disorder with a classical triad of renal tubular acidosis, intracerebral calcifications and osteopetrosis. We present a case of a 6-year and 4-months old male patient presented to our pediatric gastroenterology outpatients' clinic with parental concern of poor growth. The patient is a known case of unexplained global developmental delay, recurrent fractures and constipation since birth. As a result of the patient's hyperactivity, he hit his head with the clinic's door resulting in a cut wound. Brain computed tomography scan showed abnormal symmetrical calcifications seen in both basal ganglia, thalami and subcortical white matter associated with increased bone density of the skull and upper cervical spine reassembling osteopetrosis. The suspicion of carbonic anhydrase II deficiency was confirmed by arterial blood gases revealing a marked metabolic acidosis fulfilling the diagnostic triad. The patient was discharged on sodium bicarbonate therapy, lactulose and vitamin D supplements and has been followed up regularly.