Abstract
Objective: KCNT2 gene mutations had been described to cause developmental and epileptic encephalopathies (DEEs). In this study, we presented the detailed clinical features and genetic analysis of two unrelated patients carrying two de novo variants in KCNT2 and reviewed eight different cases available in publications.Methods: Likely pathogenic variants were identified by whole exome sequencing; clinical data of the patients were retrospectively collected and analyzed.Results: Our two unrelated patients were diagnosed with Ohtahara syndrome followed by infantile spasms (IS) and possibly the epilepsy of infancy with migrating focal seizures (EIMFS), respectively. They both manifested dysmorphic features with hirsute arms, thick hair, prominent eyebrows, long and thick eyelashes, a broad nasal tip, and short and smooth philtrum. In the eight patients reported previously, two was diagnosed with IS carrying a ‘change-of-function' mutation and a gain-of-function mutation, respectively, two with EIMFS-like carrying a gain-of-function mutation and a loss-of-function mutation, respectively, one with EIMFS carrying a loss-of-function mutation, three with DEE without functional analysis. Among them, two patients with gain-of-function mutations both exhibited dysmorphic features and presented epilepsy phenotype, which was similar to our patients.Conclusion: Overall, the most common phenotypes associated with KCNT2 mutation were IS and EIMFS. Epilepsy phenotype associated with gain- and loss-of-function mutations could overlap. Additional KCNT2 cases will help to make genotype-phenotype correlations clearer.
Highlights
Developmental and epileptic encephalopathies (DEEs) comprise a heterogeneous group of sever neurological disorders with onset in infancy and childhood, which is characterized by refractory seizures, frequent epileptic activity, and developmental regression or further slowing (Scheffer et al, 2017)
We presented the detailed clinical features and genetic analysis of two unrelated patients with KCNT2related DEE and provided a comprehensive outline of available publications regarding KCNT2 mutations
Our data further expanded the spectrum of KCNT2 mutation
Summary
Developmental and epileptic encephalopathies (DEEs) comprise a heterogeneous group of sever neurological disorders with onset in infancy and childhood, which is characterized by refractory seizures, frequent epileptic activity, and developmental regression or further slowing (Scheffer et al, 2017). A systematic review of neurological disorders and potassium channelopathies revealed pathogenic variants in 19 potassium channel genes, including. Pathogenic variants in KCNT2 gene that encodes the KNa1.2 subunit (Slick or Slo2.1) have been identified in eight cases (Gururaj et al, 2017; Ambrosino et al, 2018; Alagoz et al, 2020; Inuzuka et al, 2020; Mao et al, 2020). We reported two de novo KCNT2 variants in two unrelated patients diagnosed with DEE charactering by profound developmental delay and intractable infantile-onset seizure disorders
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