Patient 4 was a boy aged 7 years and 8 months. He achieved the gross motor developmental milestones somewhat delay, with rising head at 1 year old, sitting alone at 1 year and 2 months, and walking at 1.5 years. Lack of speech was another problem, that he still cannot speak a single word so far (7 years and 8 months). He was always immersed in his own world, showed little interest to the others, and lacked eye-contact. Febrile seizures attacked at 1 year, which turned into afebrile seizures at 2 years old. Partial seizures occurred 1~ 2 times per month, lasted few minutes to more than half an hour. The epilepsy was fever-sensitive. VPA was used at 2.5 years of age, and no seizures occurred after 4 years of age. EEG at 2.5 years displayed (multi-) spike and slow waves at right occipital region, with slow rhythm on the background. MRI at 3 years of age was normal. A novel mutation, c.403-1G > T, of MEF2C was identified, which arose de novo.
Patient 2 is a 2.5 years old girl presented with RTT-like ID. she displayed profound psychomotor retardation, with controlling head at 5 months, sitting alone at 8 months. She remained unable to walk independently and still had no speech at 2.5 years old. She developed stereotypic hand movements and bruxism at 2 years of age. No seizure was reported, but there was epileptiform discharge on EEG at age of 2 years. Brain MRI revealed high T1 and T2 signal at posterior horn of bilateral ventricle. A nonsense mutation, c.565C > T, p.Arg189*, of MEF2C was discovered, a known disease causing mutation ().