Fetal Compound Heterozygous Microdeletion at 7q31.1 Involving IMMP2L: Case Report and Literature Review

Copy number variations (CNVs) represent a significant genetic etiology for birth defects. Reports on microdeletions involving the 7q31.1 region remain scarce in the literature, with existing studies primarily documenting heterozygous deletions. Compound heterozygous chromosomal deletions inherited from non-consanguineous parents are exceptionally rare in clinical diagnostics, rendering prenatal diagnosis and genetic counseling for compound heterozygous 7q31.1 microdeletions particularly challenging.

We report the first case of a homozygous 7q31.1 microdeletion inherited from both unaffected, non-consanguineous parents. While karyotyping showed a normal chromosomal result, Copy number variation sequencing (CNV-Seq) detected a homozygous microdeletion at 7q31.1. The deletion was subsequently validated as a compound heterozygous deletion by mate-pair sequencing, and its precise breakpoints were identified through Sanger sequencing. This deletion involves exons 1, 2, and 3 of the IMMP2L gene. No abnormalities were detected on prenatal ultrasound, and no obvious abnormal phenotypes were observed during immediate postnatal examination or at the 4-month follow-up. However, the patient should currently be considered asymptomatic at this early developmental stage, and the long-term consequences of biallelic IMMP2L loss in humans remain unknown.

The combination of prenatal ultrasound, karyotype analysis, CNV-seq, mate-pair sequencing, and genetic counseling facilitates precise prenatal diagnosis of chromosomal microdeletions and microduplications. Our case can be helpful for managing the challenges of prenatal diagnosis and genetic counseling associated with CNV of uncertain clinical significance.