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 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 ().