Patient 3 is a 23-month-old girl who presented with RTT-like features. Feeding difficulties caused concern at 3 months of age. No epilepsy was observed, though she had medical history of febrile convulsions at 9 months old. There was significant delay in her developmental milestones, without obvious retrogression. She could sit alone at 1 year old, and walk at 23 months of age, with abnormal gaits. Unmeaningful language began at 12 months. She also presented with poor eye contact, stereotypic actions, breathing disturbance, and sleeping abnormalities. She suffered from recurrent respiratory infections frequently after 15 months of age. MRI revealed hypomyelination at 1 year and 10 months of age. A novel nonsense mutation, c.334G > T, p.Glu112*, in MEF2C was identified.
Patient 7 is a female who is currently 2 years 5 months old. She experienced severe hypotonia at infancy and was observed to have developmental delay. She was incapable of both lifting her head at the age of 7 months and sitting independently at the age of 2 years; she was also unable to walk independently, demonstrated no non-verbal communication skills, and was unable to imitate or babble. Poor eye contact as well as head-shaking and hand-clapping behavior were observed at the age of 1 year. She did not display purposeful hand usage. She did not experience seizure. EEG test conducted at the age of 2 years revealed 2–3 Hz sharp-slow waves at the left parietal-occipital region. MRI scans taken at the age of 14 months showed malformation of the corpus callosum, delayed myelination and leukomalacia in the periventricular region ().