Prenatal diagnosis of a 4.5-Mb deletion at chromosome 4q35.1q35.2: Case report and literature review

Prenatal Diagnosis of Fetuses with 4q35 Deletion: Case Series and Review of the Literature

INTRODUCTION

4q35 deletion is a rare chromosomal syndrome with a wide range of phenotypes, which can be challenging to detect through prenatal ultrasound. This study aimed to summarize the fetal phenotypes of patients with 4q35 deletion.

CASE PRESENTATION

The study included four fetuses with 4q35 deletion, with detailed records of prenatal ultrasound and genetic testing results. These cases included following phenotypes, fetal growth restriction (FGR) (2/4), cystic hygroma (2/4), single umbilical artery (1/4), and fused kidney (1/4). One case was terminated, while the other three were born and showed no obvious abnormalities at the 1-year follow-up. Previous reports have described the fetal phenotype of 4q35 deletion in 6 patients from five families, with prenatal phenotypes including FGR (2/6), cardiac structural abnormalities (1/6), brain ventriculomegaly (1/6), oligohydramnios (1/6), and multicystic dysplastic kidneys (1/6).

CONCLUSION

Overall, the phenotypes of fetuses with 4q35 deletion are diverse, with FGR potentially being a significant phenotype in these cases.

Optical Genome Mapping Identifies a Novel Unbalanced Translocation Between Chromosomes 4q and 6q Leading to Feeding Difficulties and Hypotonia in a Neonate: A Case Report

Optical Genome Mapping (OGM) technology has garnered growing interest for the identification of chromosomal structural variations (SVs), particularly complex ones that are implicated in genetic diseases in humans. In this study, we performed genetic diagnostics on a neonatal patient who presented with feeding difficulties, hypotonia, and an atrial septal defect. We utilized a combination of trio-whole exome sequencing and OGM for our analysis. The results revealed an unbalanced translocation between maternal chromosomes 4 and 6 in the proband, ogm[GRch38]t(4:6)(q35.2;q25.3), resulting in a 2.8 Mb deletion at the 4q35 terminal and a 10.2 Mb duplication at the 6q25 terminal. In summary, this study highlights how OGM, in conjunction with other genetic approaches, can unveil the genetic etiology of complex clinical syndromes. Neonatal patients often exhibit low specific phenotypes, underlining the significance of SV detection.

Identification of a novel isolated 4q35.2 microdeletion in a Chinese pediatric patient using chromosomal microarray analysis: a case report and literature review

BACKGROUND

Isolated terminal 4q35.2 microdeletion is an extremely rare copy number variant affecting people all over the world. To date, researchers still have controversial opinions and results on its pathogenicity. Here, we aim to present a Chinese pediatric patient with terminal 4q35.2 microdeletion and use this case to clarify the underlying genotype-phenotype correlation.

METHODS

A 17-year-old boy from Quanzhou, South China, was recruited as the main subject in this study. Karyotype and single-nucleotide polymorphism (SNP) based microarray analysis were carried out to detect chromosomal abnormalities and copy number variants in this family. Trio whole exome sequencing (Trio-WES) was performed to investigate the potential pathogenic variant in this family.

RESULTS

During observation, we identified abnormal clinical phenotypes including upper eyelid ptosis, motor developmental delay, abnormal posturing, abnormality of coordination, attention deficit hyperactivity disorder, and involuntary movements in the patient. SNP array analysis results confirmed a case of 2.0 Mb 4q35.2 microdeletion and parental SNP array verification results indicated that the terminal 4q35.2 microdeletion was inherited from his mother. No copy number variants were detected in his father. In addition, the trio-WES results demonstrated none of pathogenic or likely pathogenic variants in the patient.

CONCLUSIONS

This study brings a novel analysis of a case of 2.0 Mb terminal 4q35.2 microdeletion affecting a Chinese individual. In addition, additional clinical symptoms such as upper eyelid ptosis and involuntary movements were first reported to affect a patient with terminal 4q35.2 microdeletion, which may broaden the phenotype spectrum of the condition.