Challenges in the management of an ignored cause of hyperammonemic encephalopathy: pyruvate carboxylase deficiency.

Pyruvate carboxylase (PC) deficiency is a rare autosomal recessive disease and provides clinics in three essential phenotypes. Type B PC deficiency is characterized by lactic acidosis and hyperammonemia. We report a Turkish patient who was diagnosed with type B PC deficiency. Despite the application of anaplerotic treatment with biotin, citrate and arginine-aspartate, continuous veno-venous hemodialysis (CVVHD) treatments were applied due to the failure to keep hyperammonemia and lactic acidosis under control. Ammonia values increasing to 860 µmol/L were observed. A homozygous novel variant was detected in PC gene analyses containing a 12-base pair deletion on exon 8. Although the mutation found was not reported previously, it was accepted as a pathogenic variant due to its presence in a functional region of the protein. In type B PC deficiency, although a high level of ammonia is expected, it rarely exceeds 200 µmol/L. As far as we know, the present case has the highest ammonia values in the literature. This paper has been shared to highlight to keep PC deficiency in mind regarding the differential diagnosis of hyperammonemia, particularly in the presence of lactic acidosis, and to serve as a model for the use of different modalities in the management process of PC deficiency.