Introduction : Acute necrotizing encephalitis(ANE) is a rare disease with rapid onset of fever, seizures and decreased consciousness after viral infection. Ran-binding protein 2gene ( RANBP2 ) mutations are associated with genetic and recurrent ANE. Brain magnetic resonance imaging feature is characterized by involving thalami, brainstem, cerebellum and white matter symmetrically. CASE1 : A previous healthy 18-month-old girl was admitted for fever, decreased activity and altered mental status. MRI showed T2 high signal intensity in both ganglia, Lt thalamus, dentate nucleus and tegmentum of brain stem. The patient was treated with anticonvulsants, antivirals and empiric antibiotics. We started treatment with IV methylprednisolone for 10 days. The child showed improving 8 days. A subsequent MRI scan performed 1 month later revealed improvement. However, the child has quadreplegic cerebral palsy as a complication. And she undergoing rehabilitation and is being followed up at the outpatient clinic. There is a positive results to the RANBP2 gene on a blood test after discharge. CASE2 : A 3-year-old girl visited the emergency room with seizure for 30 minutes and rapidly progressed to stuporous mental status. The patient had a history of ANE at 11 months of age. Since then, she has been in good health without any complications. Five days before admission, she had a fever of up to 40℃. On the day before admission, a generalized weakness began, and there were episodes of vomiting. The neurological examination revealed increased motor tone and deep tendon reflexes and positive bilateral Barbinski reflexes, and showed decorticated posturing. Laboratory results and CSF test were normal. Brain MRI revealed hypointense on T1 and hyperintense on T2 in thalamus,hypothalamus, mibrain, pons, medulla, were similar to the previous locations. We started on IV methylprednisolone therapy for 4 weeks and administered antibiotic therapy and acyclovir. After one month, MRI showed improvement. However, cognitive and motor function were not recovered. RANBP 2 gene performed during admission revealed a negative results. The patient is undergoing rehabilitation. Results : We report a case of ANE who had a RANBP2 gene-mutation and a case of recurrent ANE.