Chromosomal microarray and exome sequencing in unexplained early infantile epileptic encephalopathies in a highly consanguineous population


TÜRKDOĞAN D., Turkyilmaz A. , Sager G., Ozturk G., ÜNVER O., Say M.

INTERNATIONAL JOURNAL OF NEUROSCIENCE, 2021 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Publication Date: 2021
  • Doi Number: 10.1080/00207454.2021.1967349
  • Title of Journal : INTERNATIONAL JOURNAL OF NEUROSCIENCE
  • Keywords: Early infantile epileptic encephalopathies, chromosomal microarray, whole exome sequencing, candidate genes, targeted therapy, recessive inheritance, DE-NOVO MUTATIONS, GENETICS, EPILEPSIES, VARIANTS, SEIZURES, DELETION

Abstract

Aim To identify genetic causes for early infantile epileptic encephalopathies (EIEE) in Turkish children with mostly consanguineous parents. Methods In a selected EIEE group (N = 59) based on results of nongenetic and initial genetic testing with unexplained etiology, 49 patients underwent array-based comparative genomic hybridization (aCGH) and 49 patients underwent whole exome sequencing (WES) including 39 with negative aCGH results and 10 with WES-only. Results Diagnostic yield of aCGH and WES for pathogenic or likely pathogenic variants was 14.3% and 38.8%, respectively. Including de novo variants of uncertain significance linked to compatible phenotypes, increased the diagnostic yield of WES to 61.2%. Out of 38 positive variants, 18 (47.4%) were novel and 16 (42.1%) were de novo. Twenty-one (56.8%) patients had recessive variants inherited from mostly consanguineous healthy parents (85.7%). Fourteen (37.8%) of patients with diagnostic results had positive variants in established EIEE genes. Seizures started during neonatal period in 32.4% patients. Posture or movement disorders were comorbid with EIEE in 40.5% of diagnosed patients. We identified treatable metabolic disorders in 8.1% of patients and pathogenic variants in genes which support using targeted medicine in 19% of patients. Conclusions Detailed electro-clinical phenotyping led to expansion of some of the known phenotypes with non-neurological and neurological findings in addition to seizures, as well as suggestion of candidate genes (SEC24B, SLC16A2 and PRICKLE2) and a copy number variant (microduplication of Xp21.1p11.4). The high ratio of recessive inheritance could be important for family counseling.