# Case Report: A family with X-linked ichthyosis identified by secondary findings of non-invasive prenatal testing

## TL;DR

A family with X-linked ichthyosis was identified through a prenatal test that found a genetic deletion linked to the condition.

## Contribution

This case highlights how NIPT can uncover genetic deletions relevant to hereditary diseases in families.

## Key findings

- NIPT detected a 2 Mb deletion at Xp22.31, including the STS gene, in a pregnant woman.
- The deletion was confirmed by chromosome microarray analysis and linked to XLI in family members.
- CNVs identified by NIPT can predict pathogenic variations in the fetus and family genome.

## Abstract

We report a family with X-linked ichthyosis (XLI), in which the non-invasive prenatal testing (NIPT) results from the pregnant woman revealed a deletion of approximately 2 Mb at Xp22.31, confirmed by chromosome microarray analysis. This deletion includes the steroid sulfatase (STS) gene, which is responsible for XLI, and clinical features of XLI were also found in family members. XLI is a recessive hereditary skin disease characterized by deep brown polygonal scales, and its clinical manifestations are not obvious, making genetic diagnosis difficult for patients. The incidental findings from this NIPT suggest that copy number variations (CNVs) detected by NIPT can help predict pathogenic CNVs in the fetus and even in the entire family genome. We should pay more attention to CNVs identified by NIPT during prenatal screening.