Paraneoplastic encephalitis encompasses a diverse spectrum of neurological disorders associated with a variety of pediatric tumor types.

We describe a seven-year-old boy with paraneoplastic necrotizing encephalitis associated with precursor B-cell acute lymphoblastic leukemia.

The initial presentation involved acute-onset upper extremity weakness, seizure-like activity, and agitation. Extensive evaluation revealed pancytopenia, elevated protein in the cerebrospinal fluid, and normal magnetic resonance imaging (MRI) consistent with a clinical diagnosis of encephalitis of presumed viral etiology. He was treated with antimicrobials and intravenous immunoglobulin and returned to his neurological baseline before discharge. One month later, he was diagnosed with precursor B-cell acute lymphoblastic leukemia. Before chemotherapy initiation, he again became encephalopathic. Repeat cerebrospinal fluid evaluation showed elevated protein, and MRI revealed findings consistent with diffuse necrotizing encephalitis. He received standard chemotherapy as well as immunotherapy with intravenous immunoglobulin and plasmapheresis, with resolution of MRI abnormalities and improvement in neurological status. At six years postpresentation, he is in remission for acute lymphoblastic leukemia, without significant neurocognitive deficits and mild right spastic hemiparesis.

This is the first report of paraneoplastic encephalitis associated with pediatric leukemia. A hematologic malignancy should be considered in the differential diagnosis of paraneoplastic encephalitis.