Bilateral Symmetrical Brain MRI Findings in Acute Necrotising Encephalopathy Type 1

<b>Background:</b> Acute necrotising encephalopathy (ANE) is a rare and severe type of encephalopathy with bilateral symmetrical brain lesions, often following a viral prodrome. ANE type 1 (ANE1) is a disease subtype with a predisposing mutation in the gene encoding RAN binding protein 2 (<i>RANBP2</i>). <b>Methods:</b> We report a case of a 3-year-old girl with clinical symptoms of ANE and brain MRI findings suggesting ANE1, which was subsequently confirmed by genetic analysis. <b>Results:</b> MRI of the brain demonstrated symmetrical high T2/FLAIR signal changes in the lateral geniculate bodies, claustrum, ventromedial thalami, subthalamic nuclei, mamillary bodies, and brainstem, with partly corresponding diffusion restriction, as well as additional haemorrhagic changes in the lateral geniculate bodies on susceptibility weighted imaging. Genetic analysis revealed a heterozygous pathogenic variant of the <i>RANBP2</i> gene. With immunosuppressive and supportive treatment, the patient fully recovered and was discharged after 10 days in the hospital with no residual symptoms. <b>Conclusions:</b> Recognition of the characteristic MRI findings in ANE1 can facilitate a timely diagnosis and enhance the clinical management of the patient and their relatives, especially given the high risk of disease recurrence.