Whole exome sequencing identified a homozygous novel mutation in SUOX gene causes extremely rare autosomal recessive isolated sulfite oxidase deficiency and literature review

Abstract Background: Isolated sulfite oxidase deficiency (ISOD) is the rarest types of life-threatening neurometabolic disorders characterized by neonatal intractable seizures and severe developmental delay with an autosomal recessive mode of inheritance. ISOD is extremely rare and till date only 32 mutations have been identified and reported worldwide. Germline mutation in SUOX gene causes ISOD. Methods: Here, we investigated a 5-days old Chinese female child, presented with intermittent tremor or seizures of limbs, neonatal encephalopathy, subarachnoid cyst and haemorrhage, dysplasia of corpus callosum, neonatal convulsion, respiratory failure, cardiac failure, hyperlactatemia, severe metabolic acidosis, hyperglycemia, hyperkalemia, moderate anemia, atrioventricular block and complete right bundle branch block. Results: Whole exome sequencing identified a novel homozygous transition (c.1227G>A) in exon 6 of the SUOX gene in the proband. This novel homozygous variant leads to the formation of a truncated sulfite oxidase (p.Trp409*) of 408 amino acids. Hence, it is a loss-of-function variant. Proband’s father and mother is carrying this novel variant in a heterozygous state. This variant was not identified in 200 ethnically matched normal healthy control individuals. Conclusions: Our study not only expand the mutational spectrum of SUOX gene associated ISOD, but also strongly suggested the application of whole exome sequencing for identifying candidate genes and novel disease-causing mutations.