Abstract: Objective? To explore the clinical and genetic variation characteristics of asparagine synthetase deficiency (ASNSD). Method The clinical data of ASNSD in a child was analyzed and relevant literature was reviewed. Results A 5 -year- 3 -month-old girl presented with severe psychomotor retardation and recurrent seizures. Cranial MRI showed supratentorial ventricular dilatation, brain atrophy and thin corpus callosum. Whole exome sequencing showed that there were compound heterozygous variants in the ASNS gene of the child, which were the codon variant of c. 1503 _ 1505 delAGC from the father and the missense variant of c. 776 G>C from the mother. The mutation was reported for the first time, and bioinformatics softwares (Provean and mutationtaster) predicted that it was pathogenic. Conclusion? Gene detection is helpful for the diagnosis of ASNSD, and the gene variation spectrum of ASNSD was expanded in this case.

Key words: asparagine synthetase deficiency;? ASNS gene; gene mutation