2023 Volume 28 Issue 1 Pages 39-
Introduction: We present a pediatric patient with three recurrent episodes of mild encephalopathy with reversible splenial lesion (MERS) caused by different infections over a 3-year period.
Case presentation: The patient was a 13-year 10-month-old boy with no abnormal findings in his birth or developmental history. He had three febrile seizures and frequent febrile delirium. (At first onset) At age 13, he developed delirium after fever and was diagnosed with influenza virus type B. Blood examinations revealed hyponatremia, and brain magnetic resonance imaging（MRI）revealed a lesion with reduced diffusion in the cerebral corpus callosum and periventricular white matter of the lateral ventricles, leading to a diagnosis of MERS type 2. Intravenous methylprednisolone (IVMP) was administered, as the patient had persistent abnormal behavior. The abnormal signals disappeared on the fifth day. (At second onset) At the age of 16 years and 5 months, he presented with fever and cough and was diagnosed with mycoplasma infection. Myoclonus-like involuntary movements of the right upper extremity were observed immediately after the onset of fever. On the second day, brain MRI showed a reduced diffusion region (type 2) at the same site as the first onset. IVMP was administered, but the involuntary movements of the right upper limb continued thereafter. On the 12th day, a second IVMP was performed, and the neurological symptoms resolved. (At the third onset) At the age of 16 years and 8 months, he presented with fever and was diagnosed with influenza virus type A. On the second day, he began to have involuntary movements of the right upper extremity. After admission, myoclonus-like seizures were observed in the right medial thigh and right face. On the second day, brain MRI revealed a reduced diffusion region in the cerebral corpus callosum (type 1), and IVMP was administered.
Conclusion: According to Japanese guidelines for the treatment of acute encephalopathy in children, aggressive therapeutic intervention is not required for MERS. However, because this patient presented with a variety of neurological symptoms, we administered medication, including IVMP, at the onset of the three episodes. Genetic background, such as the myelin regulatory factor（ MYRF ）gene abnormality, was considered one of the causes. These symptoms may repeat in the future and should be carefully monitored.
