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 6 is a male who is currently 2 years 7 months old. He was observed to have severe hypotonia in his infancy and developmental delay. He was incapable of lifting his head at the age of 5 months but could sit independently at 9 months; however, he exhibited a regression in development and was unable to walk independently. He also did not show any non-verbal communication skills and was unable to imitate or babble. Poor eye contact, head shaking, hand clapping and hand wringing were observed at the age of 1 year and 6 months. The patient displayed purposeful hand usage. He also presented recurrent, febrile or non-febrile, generalized tonic-clonic seizures at the age of 9 months. Topiramate, VPA and LEV were used but none of them showed a positive effect; this treatment was withdrawn at the age of 2 years. At present, the patient's daily seizures have been characterized as myoclonic. EEG findings obtained at the age of 10 months revealed spike-slow waves with bilateral-central-frontal involvement. MRI scans taken at the age of 15 months showed developmental malformation of the corpus callosum ().