From Overgrowth to Complex Malformations: A Novel EZH2 Variant Reveals the Expanding Clinical Spectrum of Weaver Syndrome

TL;DR

A new EZH2 gene variant in a child with Weaver syndrome reveals more severe and complex symptoms, including brain malformations and hand deformities.

Contribution

A novel EZH2 variant is identified that expands the known clinical and molecular spectrum of Weaver syndrome.

Findings

A novel EZH2 variant c.449T>C (p.Ile150Thr) was found in a patient with Weaver syndrome.

The patient exhibited severe camptodactyly and complex brain malformations not previously reported in Weaver syndrome.

The variant affects the SANT domain of EZH2, suggesting a link to the severe phenotype observed.

Abstract

Weaver syndrome is a rare congenital overgrowth disorder caused by pathogenic EZH2 variants. This study reports a novel EZH2 variant associated with atypical manifestations, including severe bilateral camptodactyly and complex brain malformations. A 4-year-old Taiwanese female exhibited classical Weaver syndrome features including macrosomia, macrocephaly, hypertelorism, and developmental delay, plus atypical findings of severe bilateral camptodactyly and complex brain malformations. Neuroimaging revealed corpus callosum dysgenesis with rostral agenesis and genu hypoplasia, bilateral frontal lobe hypoplasia, and an arachnoid cyst. The patient demonstrated global developmental delay with marked motor impairment but less severely affected speech and cognition, consistent with mild intellectual disability. Whole-exome sequencing identified a novel de novo pathogenic variant in EZH2: c.449T>C (p.Ile150Thr), affecting a highly conserved amino acid within the SANT domain. This case broadens the clinical spectrum of Weaver syndrome by highlighting severe camptodactyly and complex brain malformations as possible EZH2-related manifestations. The corpus callosum dysgenesis suggests a wider role of EZH2 in neurodevelopment than previously recognized. The novel SANT domain variant may explain the severe phenotypic presentation. The novel EZH2 variant c.449T>C (p.Ile150Thr) expands the molecular and phenotypic spectrum of Weaver syndrome. These findings underscore the importance of comprehensive neuroimaging and molecular genetic testing in suspected cases, particularly atypical presentations.

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