Carbonic anhydrase VA deficiency: a very rare case of hyperammonemic encephalopathy.

Objectives: Carbonic anhydrase VA (CAVA) deficiency is a rare autosomal recessive inborn error of metabolism that leads to acute metabolic crises, especially in the neonatal or infantile period. It is caused by a deficiency of the enzyme CAVA, which is encoded by the CA5A gene. Case presentation: Fifteen patients with homozygous pathogenic CA5A mutations involving 10 different lesions have been reported in the literature up to date. Main clinical and biochemical features of CAVA deficiency include lethargy, hyperammonemic encephalopathy, metabolic acidosis, elevated lactate and hypoglycemia. In most patients reported so far, a single metabolic decompensation attack has been reported, and they have remained stable thereafter with no further crisis. Conclusions: We report the 16th case of CAVA deficiency, who was diagnosed by whole-exome sequencing and showed a typical course of the disease with normal development at 18 months.