# A novel de novo missense variant in ASH1L associated with mild autism spectrum disorder and an uneven cognitive profile: a case report

## TL;DR

A new genetic variant in ASH1L is linked to mild autism and uneven cognitive abilities in a child.

## Contribution

This case report identifies a novel de novo missense variant in ASH1L associated with a milder neurodevelopmental phenotype.

## Key findings

- A novel de novo missense variant in ASH1L was identified in a patient with mild autism and uneven cognitive abilities.
- The variant was predicted to be damaging and is the strongest candidate to explain the patient's phenotype.
- The findings expand the phenotypic spectrum of ASH1L-related disorders and suggest milder outcomes are possible with missense variants.

## Abstract

ASH1L-related intellectual developmental disorder represents an emerging neurodevelopmental syndrome with significant phenotypic heterogeneity (Cordova et al. in Genes (Basel). 15(4):423, 2024). Comprehensive genomic analysis demonstrates superior diagnostic yield compared with targeted approaches in complex neurodevelopmental presentations (Srivastava et al. in Genet Med. 21(11):2413–2421, 2019).

This report describes a 6-year-old Central Asian (Uzbek) male patient with a history of global developmental delay who was diagnosed with mild autism spectrum disorder, attention-deficit/hyperactivity disorder, and a developmental expressive language disorder. Neuropsychological assessment revealed an uneven cognitive profile with average verbal abilities but below-average nonverbal reasoning. After uninformative targeted genetic panels, trio whole-genome sequencing identified a novel de novo heterozygous missense variant in ASH1L c.4043A > G (p.Lys1348Arg). This variant, absent in population databases, was classified as a variant of uncertain significance. However, in silico analysis predicted this variant to be probably damaging, and therefore, it emerged as the strongest candidate to explain the patient’s phenotype.

This case expands the known phenotypic spectrum of ASH1L-related disorders, demonstrating that a de novo missense variant can be associated with a milder neurodevelopmental phenotype, including borderline-to-average intellectual ability. These findings challenge suggestions that missense variants uniformly lead to more severe outcomes and underscores the importance of comprehensive genomic and deep clinical characterization to refine our understanding of gene–disease relationships.