Acute Necrotizing Encephalopathy in a Child With RANBP2 Mutation: A Case of Unanticipated Full Resolution.

Acute necrotizing encephalopathy (ANE) is a rare, rapidly progressive pediatric encephalopathy, often triggered by viral infections such as influenza A (H1N1), and typically characterized by bilateral thalamic involvement with high morbidity and mortality. We present a case of a previously healthy two-year-old girl who developed fever and respiratory symptoms, followed by sudden neurological deterioration and shock. Initial investigations revealed markedly elevated liver enzymes with normal cerebrospinal fluid analysis. Nasopharyngeal swabs tested positive for H1N1. Brain magnetic resonance imaging (MRI) revealed symmetric lesions involving the thalami and brainstem. Genetic analysis identified a heterozygous pathogenic mutation in the RANBP2 gene. Based on the clinical presentation, virologic findings, and characteristic imaging features, a diagnosis of ANE was established. The patient was promptly treated with intravenous immunoglobulin and high-dose corticosteroids, resulting in full neurological recovery within six weeks. This case underscores the importance of the early recognition and diagnosis of ANE and highlights the potential for favorable outcomes with timely immunotherapy, even in the presence of a RANBP2 mutation.