Abstract
The article presents a clinical observation of a patient with atypical absences, myoclonia, psychomotor, and speech retardation. Whole-exome sequencing of the patient’s genetic material revealed a previously undescribed mutation in the SETD1B gene. The phenotypic picture of our case is similar to the data of patients with variants in the SETD1B gene, previously described in the scientific literature. The majority of the identified mutations occur in the catalytic domains, single-electron transfer (SET) and N-single-electron transfer (N-SET). There are only 6 cases in the RNA binding domain (RNA recognition motif), accounting for 3 exons of the gene. However, regardless of the location and type of mutation, the phenotypic manifestations of the described cases have common features. We want to draw the attention of the global scientific community for further research and a better understanding of the genotype-phenotypic correlation in SETD1B-associated nervous system disorder.