Mitochondrial carbonic anhydrase VA deficiency is a rare autosomal recessive disease that can lead to hyperammoniacal encephalopathy. The reported cases had the onset of hyperammoniacal encephalopathy from newborn period（the first day of life） to early childhood（up to the age of 4 years）. It would interfere with the activities of a variety of mitochondrial enzymes and result in gluconeogenesis and aerobic oxidation disorders，branched chain amino acids catabolism and urea cycle disorders. Human mitochondrial carbonic anhydrase VA gene CA5A was originally cloned and located in 16q24.3 region in 1993，but the first case of disease caused by carbonic anhydrase VA deficiency was reported in 2014 by van Karnebeek et al. So far，only less than 30 cases have been reported world-wide，among which mostly described patients came from the South Asia，and the global incidence is unknown.
