By uncovering a pathogenic missense mutation in the HNRNPU gene, associated with HNRNPU-related neurodevelopmental disorder (HNRNPU-NDD) and developmental and epileptic encephalopathy-54 (DEE54), WES enabled a more precise understanding of the patient’s condition and provided answers for the patient and their family. This evidence concerns the gene HNRNPU and Neurodevelopmental delay.