Novel CLCN4 variant associated with syndromic X-linked intellectual disability in a Chinese girl: a case report

The Raynaud-Claes type of X-linked syndromic mental retardation (MRXSRC) is a very rare condition, by intellectual disability ranged from borderline to profound, impaired language development, brain abnormalities, facial dysmorphisms and seizures. MRXSRC is caused by variants in CLCN4 which encodes the 2Cl^-/H⁺ exchanger ClC-4 prominently expressed in brain.

We present a 3-year-old Chinese girl with intellectual disability, dysmorphic features, brain abnormalities, significant language impairment and autistic features. Brain magnetic resonance imaging (MRI) showed a thin corpus callosum, a mega cisterna magna and ventriculomegaly. Whole exome sequencing (WES) was performed to detect the molecular basis of the disease. It was confirmed that this girl carried a novel heterozygous missense variant (c.1343C > T, p.Ala448Val) of CLCN4 gene, inherited from her mother. This variant has not been registered in public databases and was predicted to be pathogenic by multiple in silico prediction tools.

Our investigation expands the phenotype spectrum for CLCN4 variants with syndromic X-linked intellectual disability, which help to improve the understanding of CLCN4-related intellectual disability and will help in genetic counselling for this family.