Data on the genetic landscape of congenital microcephaly (CM) in China are scarce, and the incidence of CM caused by the most commonly mutated gene ASPM in China remains unknown.
Sixty-one neonates with CM who were hospitalized in the Children\'s Hospital of Fudan University between August 1, 2016, and August 31, 2020, were enrolled, and the clinical data and clinical exome-sequencing data were analyzed. An additional 18,103 parental data entries from the Chinese Children\'s Genetic Testing Clinical Collaboration System database were collected to estimate the incidence of ASPM-related congenital microcephaly (ASPM-CM) in East China by analyzing the carrier frequency of ASPM mutations.
Among the 61 neonates with CM, 35 (57.4%) patients were identified with genetic findings, including 24 patients with single nucleotide variants (SNVs) and 11 patients with copy number variations (CNVs). ASPM was the most common gene with detrimental SNVs detected in 3 patients. Patients with genetic findings showed a significantly higher incidence of developmental delay (91.3%, 21/23) than those without genetic findings (60%, 9/15) (p = 0.04). All the 3 decreased patients had genetic findings. The estimated ASPM-CM incidence in East China was 1/1,295,044.
Comprehensive genetic testing, detecting both SNVs and CNVs, is recommended for newborns with CM. Patients with genetic findings should be aware of the potential for developmental delay. ASPM gene defect was the most common genetic cause of CM in this study. The estimation of the incidence of ASPM-CM in East China might provide a reference for analyzing overall incidence.

BACKGROUND: Asparagine Synthetase Deficiency (ASNSD; OMIM #615574) is a newly described rare autosomal recessive neurometabolic disorder, characterised by congenital microcephaly, severe psychomotor delay, encephalopathy and progressive cerebral atrophy. To date, seven families and seven missense mutations in the ASNSD disease causing gene, ASNS, have been published.
METHODS: We report two further affected infant sisters from a consanguineous Indian family, who in addition to the previously described features had diaphragmatic eventration. Both girls died within the first 6 months of life. Whole exome sequencing (WES) was performed for both sisters to identify the pathogenic mutation. The clinical and biochemical parameters of our patient are compared to previous reports.
RESULTS: WES demonstrated a homozygous novel missense ASNS mutation, c.1019G > A, resulting in substitution of the highly conserved arginine residue by histidine (R340H).
CONCLUSIONS: This report expands the phenotypic and mutation spectrum of ASNSD, which should be considered in neonates with congenital microcephaly, seizures and profound neurodevelopmental delay. The presence of diaphragmatic eventration suggests extracranial involvement of the central nervous system in a disorder that was previously thought to exclusively affect the brain. Like all previously reported patients, these cases were diagnosed with WES, highlighting the clinical utility of next generation sequencing in the diagnosis of rare, difficult to recognise disorders.