# Congenital Anomalies in a Neonate With Partial Monosomy of Chromosome 21 q Arm: A Case Report

## TL;DR

A neonate with multiple congenital anomalies had a genetic abnormality identified through whole-genome sequencing, revealing partial monosomy in chromosome 21.

## Contribution

The study highlights the effectiveness of whole-genome sequencing in diagnosing complex genetic abnormalities in congenital anomalies.

## Key findings

- The neonate had a partial monosomy in the 21q22.11-q22.3 region of chromosome 21.
- Whole-genome sequencing identified copy number variations and structural abnormalities.
- The case demonstrates mitotic instability with ring chromosome 21 and deletions in the q arm.

## Abstract

Congenital anomalies are a major cause of infant morbidity and mortality. Whole-genome sequencing provides a potential tool for solving diagnostic dilemmas in such instances. We report an interesting case of a neonate from India with holoprosencephaly and multiple associated anomalies, including dysmorphic features and ventricular septal defect. Karyotype analysis revealed mitotic instability. Both ring chromosome 21 and deletions in the q arm of chromosome 21 were observed in the metaphase spreads. To characterize the genomic abnormality more precisely, whole genome sequencing was performed, which identified a partial monosomy involving the 21q22.11-q22.3 region. This case demonstrates how whole-genome sequencing effectively identifies copy number variations and complex structural abnormalities, providing valuable insights into the genetic basis of congenital abnormalities.