Childhood-Onset Epileptic Encephalopathy Due To Fgf12 Exon 1-4 Tandem Duplication

Fibroblast growth factor 12 (FGF12) spans 5 exons and encodes for a cytosolic voltage-gated sodium channel binding protein that modulates neuronal excitability.(1,2) A recurrent activating FGF12 mutation (NM_021032, [GRCh37] 192053223C>T, p.R114H in A-isoform, p.R52H in B-isoform) causes epileptic encephalopathy (EE) with neonatal onset and intellectual disability (ID).(2-6) Recently, a tandem duplication involving exons 1-4 of the FGF12 gene was related to a later onset EE phenotype.(7) Here, we characterize a second case harboring a FGF12 exon 1-4 duplication.