Patient 1 is a girl aged 5 years and 9 months, the first child of a healthy nonconsanguineous couple. Her psychomotor milestones were profoundly delayed, with raising head at 8 months, sitting alone at 1 year old, and still unable to walk by herself at 5 years and 9 months. Poor eye contact, hand clapping, hand wringing and bruxism were observed at 1 year old, followed by deterioration of hand skills. Epileptic attack occurred at 20 months old, and she responded to valproate (VPA), oxcarbazepine (OXC), and topiramate (TPM) combined therapy. Seizure free was achieved at 5.5 years old. EEG demonstrated spike-slow waves at right medial and posterior temporal, with generalization. MRI (1 year old) revealed enlargement of frontal subarachnoid space. Above manifestations led to the diagnosis of typical RTT. However, mutational analysis of MECP2, CDKL5 and FOXG1 was negative. Through this study, a de novo missense MEF2C mutation, c.48C > G, p.Asn16Lys, was identified, which was a novel mutation.
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 ().