Expanding the electro-clinical phenotype of associated neuroregression.

Biallelic variants in (Cysteinyl-tRNA synthetase 2; MIM*612800), are known to cause combined oxidative phosphorylation deficiency 27 (MIM#616672), characterized by severe myoclonic epilepsy, neuroregression and complex movement disorders. To date, six individuals from five families have been reported with variants in . Herein, we present an 11-year-old boy who presented with neuroregression, dysfluent speech, aggressive behavior and tremors for 2 years. An electroencephalogram (EEG) revealed a highly abnormal background with generalized spike-and-wave discharges suggestive of Electrical Status Epilepticus during Sleep (ESES). A known homozygous c.655G > A(p.Ala219Thr) pathogenic variant in exon 6 of the (NM_024537.4) was identified on exome sequencing. Our report expands the electro-clinical spectrum of the phenotype with presence of severe behavioral abnormalities, continuous tremors and ESES pattern on EEG, not previously reported.