NTRK2-related developmental and epileptic encephalopathy: Report of 5 new cases.

Abstract Purpose This study aimed to describe the phenotype of five new cases of NTRK2-related developmental and epileptic encephalopathy (DEE). Methods The clinical features, EEG, neuroimaging and genetics were reviewed for cases with likely pathogenic and pathogenic NTRK2 variants and then summarized. Results Five cases of NTRK2-related DEE were identified. Four had a previously described recurrent variant in NTRK2 and one had a novel variant. The phenotype was characterized by early- onset seizures (infantile spasms, later evolving to multifocal seizures), global developmental delay, variable movement disorders, microcephaly and optic nerve hypoplasia. Conclusions This series further expands our knowledge of the phenotype and genotype of NTRK2-related DEE.