# Prenatal Diagnosis of 6q Terminal Deletion Associated with Coffin–Siris Syndrome: Phenotypic Delineation and Review

## TL;DR

This paper reports a prenatal diagnosis of a 6q terminal deletion linked to Coffin–Siris Syndrome and highlights key clinical features associated with this rare genetic condition.

## Contribution

The study provides a detailed phenotypic delineation of 6q25.3 deletions involving the ARID1B gene and their association with Coffin–Siris Syndrome.

## Key findings

- Facial gestalt, hypertrichosis, and fifth fingernail aplasia/hypoplasia are key features of CSS linked to 6q25.3 deletions.
- Vertebral defects and cystic hygroma are additional clinical signs associated with ARID1B gene deletions.
- Prenatal diagnosis of 6q terminal deletion can lead to early identification of Coffin–Siris Syndrome.

## Abstract

Chromosome 6q deletion syndrome is a rare entity that has a highly variable clinical presentation and size of deletions. The most frequent manifestations of 6q terminal deletion are intellectual disability, facial dysmorphism, brain structural anomalies, and congenital heart defects. The phenotype is not clinically recognizable, except in those who harbor a terminal 6q deletion that includes the ARID1B gene, in whom features similar to Coffin–Siris syndrome (CSS) can be observed. We report the case of a female newborn with a prenatal diagnosis of a terminal deletion on 6q25.1q27, which encompasses the ARID1B gene, and who was diagnosed with CSS during the neonatal period. From our review, we found that facial gestalt, hypertrichosis, and fifth fingernail aplasia/hypoplasia, along with other features, such as vertebral defects and cystic hygroma (or webbed neck), correlated with the presence of a CSS causally related to 6q25.3 small deletions that include the ARID1B gene.