Correspondence

Neurodevelopmental disorder associated with IRF2BPL gene mutation: Expanding the phenotype?

IRF2BPL is an intronless gene that was mapped to 14q24.3 chromosome in 2000 and codes for the interferon regulatory factor 2 binding like protein.

To analyses the clinical characteristics of the patients reported in the literature and of an additional patient we observed in order to better delineate the phenomenological spectrum of the disease and provide indications to improve clinical recognition and facilitate diagnosis.

We reported on 28 patients carrying the IRF2BPL mutation who were identified in 10 papers (n.27), using PUBMED as the search engine, and in our hospital (n. 1).

All patients shared developmental delay/regression. Additional neurological symptoms were present in a large proportion of patients and reflected the involvement of five main neurological domains, i.e. epilepsy, dystonia, ataxia, spasticity, and ocular disturbances. Correlation analysis suggested a significant positive correlation between the number of affected neurological domains and the presence of MRI abnormalities (rho = 0.45, p = 0.02), while no significant correlation emerged between the number of affected clinical domains and age at disease onset (rho = 0.18, p = 0.35) or variant type (rho = 0.30, p = 0.12).

Our analysis highlights that the IRF2BPL mutation syndrome is highly specific to the central nervous system. Diagnostic work-up should consider the clinical picture of the IRF2BPL mutation syndrome herein delineated and the existence of conditions that share developmental delay/regression and result from acquired/genetic or unidentifiable underlying etiology.

Pathogenic variants of the IRF2BPL gene have been mostly associated with early onset epileptic encephalopathy. Movement disorders such as dystonia and ataxia were also reported, with symptoms mainly developing between childhood and adolescence. Here we describe a family with several members affected by a late onset dystonic and ataxic progressive syndrome, caused by a novel heterozygous pathogenic variant in the IRF2BPL gene.

Mutations in the IRF2BPL gene can cause neurodevelopmental disorders. We describe the clinical and genetic characteristics of a Chinese patient with a novel abnormality in this gene, explore the potential pathogenic mechanism and summarize the clinical characteristics of 25 patients with IRF2BPL mutations.

We identified the gene mutation sites by whole-exome and Sanger sequencing. The protein-protein interaction network of the IRF2BPL gene was constructed using bioinformatic techniques, and its function was enriched. We conducted a functional experiment to explore the potential pathogenicity of the identified IRF2BPL gene mutation.

An 8-year-old girl presented with progressive cerebellar ataxia, including involuntary tremor and slurred speech. Electroencephalography and electromyography revealed no abnormalities. Structural cranial MRI was also normal, but genetic analysis identified a truncating de novo variant in IRF2BPL. Bioinformatics predicted that IRF2BPL would be associated with IRF2 and 10 other genes and involved in ubiquitin binding and other pathways. The cellular location of IRF2BPL was altered, and compared to control cells, the level of ubiquitinated proteins was significantly decreased in cells harbouring the mutation.

In this study, we identified a truncating de novo variant of IRF2BPL as a causative gene in the neurodevelopmental disorder of a Chinese girl. Impairment of the ubiquitin-proteasome pathway caused by this IRF2BPL mutation may play an important role in this neurodevelopmental disorder.