The responsible splice variant(s) were proposed to be either FGF13-V, FGF13-VY, and FGF13-Y that were lost in two affected brothers who inherited a maternal balanced translocation that disrupts FGF13 on the X-chromosome and preserves the FGF13-S and the FGF13-U splice variants (Puranam, He et al. 2015) or, in contrast, FGF13-S in a series of unrelated individuals presenting with DEE symptoms (Fry, Marra et al. 2021). Here, FGF13 is linked to developmental and epileptic encephalopathy.