Patient 1 is a 5-year-old girl, who was observed to have severe hypotonia in her infancy and developmental delay. She was incapable of lifting her head when she was 7-month-old as well as was incapable of sitting by herself and had trouble imitating speech or actions when she was 1-year-old. By the age of 14 months, she was found to lack the ability to maintain eye contact and displayed head-shaking, hand-clapping and hand-wringing as well as bruxism. While she exhibited purposeful hand use, she presented recurrent, febrile or non-febrile, generalized tonic-clonic seizures at the age of 18 months. After receiving treatment with Levetiracetam (LEV) at 20 months, she achieved seizure-free status at the age of 2 years. At the age of 18 months and 2 years, the findings of her EEG tests revealed spike-and-slow waves with bilateral temporal involvement. Her MRI findings at the age of 14 months indicated a widened subarachnoid space ().
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 ().