ASNS deficiency is an autosomal recessive neurometabolic disorder of asparagine biosynthesis.  Affected patients display failure to thrive, microcephaly, delayed psychomotor development, progressive encephalopathy, and seizures.  Moreover, patients may experience an early death due to the disease severity.  The disorder may present in utero or at birth.  

The prevalence of the condition is less than 1 in 1,000,000 live births.  Diagnosis can be achieved through careful clinical examination, brain MRI, and biochemical analysis, which shows low level of asparagine, and molecular genetic testing.  Treatment is symptomatic.

Mutations in the ASNS cause ASNSD.  The ASNS gene, located on the long arm of chromosome 7 codes for an asparagine synthetase enzyme which is involved in the synthesis of asparagine from glutamine and aspartate.  The absence of a functional enzyme results in a deficiency of asparagine, especially in the brain and CSF.