A Novel KMT2E Splicing Variant as a Cause of O'Donnell-Luria-Rodan Syndrome With West Syndrome: Expansion of the Phenotype and Genotype.

Introduction: O'Donnell-Luria-Rodan (ODLURO) syndrome is an autosomal dominant disorder associated with KMT2E gene variants. ODLURO syndrome is characterized mainly by developmental delay, intellectual disability and macrocephaly or microcephaly; in some patients, it may manifest as autism or epilepsy.

Methods: Trio whole-exome sequencing was performed on a female infant with unexplained West syndrome and developmental regression. A de novo splicing variant in the KMT2E gene was identified. The effects of this variant were analysed via a minigene splice assay and in vitro reverse transcription PCR.

Results: The patient presented with spasmodic seizures and developmental delay at 6 months of age. The video electroencephalogram (EEG) displayed hypsarrhythmia. Brain MRI revealed abnormal signals around the lateral ventricles and decreased white matter volume. A novel splicing variant in the KMT2E gene (NM_182931.3: c.1248_1248+9del) was identified in our proband. Sanger sequencing confirmed that the variant was not inherited from her parents. The in vitro minigene assay confirmed that c.1248_1248+9del resulted in exon 12 skipping.

Conclusion: To our knowledge, this is the first definite report of ODLURO syndrome with West syndrome as the original manifestation. The deleterious effects of KMT2E c.1248_1248+9del were demonstrated in our proband. Splicing variants in the KMT2E gene are rare, and our study expands the phenotype and genotype of ODLURO syndrome. Additional studies are needed to explore the genotype-phenotype correlations of this disease.