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

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.