Objective: To analyze the clinical characteristics and ZBTB18 gene variant in a child with epilepsy and global developmental delay.
Methods: Clinical data and laboratory examination of the patient were reviewed. Whole exome sequencing (WES) was also carried out for the family trio.
Results: The main manifestations of the child included global developmental delay, short stature, epileptic seizures. EEG revealed frequent occurrence of sharp (slow) waves in the right central region during sleeping, with sharp waves occasionally seen in the frontal and right posterior temporal regions. Cranial MRI has shown no obvious abnormality. WES has identified a de novo pathogenic variant in the ZBTB18 gene [NM_205768.3: exon 2: c.1282_1283del (p.Phe428Leufs*72)]. Based on the guidelines from American College of Medical Genetics and Genomics (ACMG), the variant was classified as pathogenic (PS2+PVS1_Moderate+PM2_Supporting). Following treatment with levetiracetam and rehabilitation, the seizures have been controlled for nearly half a year, with improvement of the psychomotor and language development. So far 28 children have been discovered with ZBTB18 gene mutations, and there was a significant difference in the clinical phenotypes of motor retardation, language retardation and epilepsy between those harboring frameshift/nonsense mutations and missense mutations.
Conclusion: The c.1282_1283del (p.Phe428leufs *72) variant of the ZBTB18 probably underlay the autosomal dominant mental disorder type 22 in this child. Compared with missense mutations, frameshift/nonsense mutations may predispose more to motor retardation, delayed language development and epilepsy.