A unique case of hyperammonemia due to CA5A deficiency: Impact of coexisting gene mutations, pseudogene, and microdeletion.

Carbonic anhydrase 5A (CA5A) belongs to a family of carbonic anhydrases which are zinc metalloenzymes involved in the reversible hydration of CO2 to bicarbonate. Mutations in CA5A are very rare and known to cause Carbonic anhydrase 5A deficiency (CA5AD), an autosomal recessive inborn error of metabolism characterized clinically by acute onset of encephalopathy in infancy or early childhood. CA5A also has two very identical pseudogenes whose interference may result in compromised accuracy in targeted sequencing. We report a unique case of CA5AD caused by compound heterozygous variant (NM_001739.2: c.721G>A: p.Glu241Lys & NM_001739.2: c.619-3420_c.774 + 502del4078bp) in an infant in order to expand the phenotypic spectrum and underscore the impact of pseudogenes, which can introduce complexities in molecular genetic analysis.