ASNS and congenital microcephaly - severe encephalopathy - progressive cerebral atrophy syndrome: Asparagine synthetase deficiency (ASNSD) was initially reported in 2013 [10], and since then, about 75 patients within more than 50 families have been described following whole exome sequencing to identify biallelic homozygous or compound heterozygous mutations in the ASNS gene [11].