Patient S78 presented clinically with PM (−3.7 SD), DD, epileptic encephalopathy, axial hypotonia, limb hypertonia and EEG abnormalities and has a homozygous mutation NM_024596.5: c.664T>C: p.(Cys222Arg) in the MCPH1 gene inherited from carrier parents and a heterozygous de novo variant NM_014191.4: c.5630A>G: p.(Asn1877Ser) in the SCN8A gene. The gene discussed is SCN8A; the disease is Epileptic encephalopathy.