OBJECTIVETo study the clinical features of early-onset epileptic encephalopathies (EEEs) of unknown cause, and to identify pathogenic microdeletion/microduplication of EEEs by genome-wide analysis of copy number variations (CNVs).

METHODSThe clinical data of 60 children diagnosed with unexplained EEEs between July 2012 and April 2013 were obtained and analyzed. Specimens were collected from the selected children and their parents. Single nucleotide polymorphism array was used to detect genome-wide CNVs, and fluorescence in situ hybridization was performed to verify the results and analyze the source of the parents, further to identify suspected pathogenic CNVs of EEEs.

RESULTSAmong the 60 children with unexplained EEEs, 34 were diagnosed with West syndrome, 3 with Ohtahara syndrome, 3 with Dravet syndrome, and 20 with unclassified EEEs. In total, 77% of the patients were associated with moderate to severe mental retardation. Head imaging test implied that 35% of the patients had brain dysplasia or astrophy. Among 54 patients, 17% showed microcephalus. After treatment, 28 patients had clinical seizures under control, 16 out of control, 5 dead, and 1 lost to follow-up. Genome-wide analysis of CNVs showed that 7 pathogenic or suspected pathogenic CNVs were present in 5 patients.

CONCLUSIONSEEEs of unknown cause are associated with high phenotypic heterogeneity and poor prognosis. Genome-wide CNVs analysis can demonstrate pathogenic or suspected pathogenic CNVs. This research expands the gene bank of EEEs and improves the understanding about possible etiology of unexplained EEEs. The results provide a reference for genetic counseling regarding reproduction in the patient's family.