Objective: To explore the clinical and genetic characteristics of a child with autosomal recessive primary microcephaly (MCPH).

Methods: A case study has been carried out on a boy who had presented at the Inner Mongolia Maternity and Child Health Care Hospital for microcephaly and mental deficiency in September 2022. Prenatal ultrasound images were retrospectively analyzed, and whole exome sequencing and Sanger sequencing were carried out for his family. A literature review was also carried out using keywords such as "ASPM gene", "microcephaly", "prenatal diagnosis", "primary microcephaly", "ASPM", "MCPH5", "MCPH", "autosomal recessive microcephaly", and "prenatal diagnosis on ultrasonography" on the PubMed database, Wanfang Data and China National Knowledge until September 2023. This study was approved by the Inner Mongolia Maternity and Child Health Care Hospital (Ethics No. 2021-093-1).

Results: The proband had shown progressive reduction in biparietal diameter (BPD) and head circumference (HC) during the fetal period. He was found to harbor compound heterozygous variants of the ASPM gene, which included a paternally derived c.8044C>T (p.R2682X) and a maternally derived c.8652dup (p.A2885Sfs*35). Both variants were classified as pathogenic (PVS1+PM2_Supporting+PP4; PVS1+PM2_Supporting+PM3) based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). For other fetuses in his family, prenatal ultrasound and genetic testing were all normal. Literature research has identified 11 relevant articles, which included 14 MCPH cases. All of the MCPH5 cases had shown various degrees of reduced BPD/HC on fetal imaging (100%, 15/15). Developmental delay, intellectual disability, and attention deficits were noted in all survived cases, with one case having seizures (12.5%, 1/8). Their genotypes had included homozygotes (46.2%, 6/13) and compound heterozygotes (53.8%, 7/13) for nonsense variants (45%, 9/20) and frameshifting variants (55%, 11/20).

Conclusion: The compound heterozygous variants c.8044C>T (p.R2682X) and c.8652dup (p.A2885Sfs*35) of the ASPM gene probably underlay the reduced BPD and HC in this proband with MCPH.