Child Neurology: Anti-Hu Encephalitis in an Adolescent With a Mediastinal Seminoma

Abstract

Anti-Hu antibodies are associated with autoimmune syndromes, mainly limbic encephalitis, encephalomyelitis and painful sensory polyneuropathy (Denny-Brown). We report a case of a 15-year-old boy presenting withepilepsia partialis continua(EPC) found to have a right middle frontal gyrus brain lesion without atrophy or contralateral involvement. Following partial resection, neuropathology revealed neuronal loss, reactive gliosis and astrocytosis, as well perivascular mononuclear inflammatory infiltrate and features of neuronophagia resembling Rasmussen encephalitis. Suboptimal response to antiseizure drugs and surgery prompted further workup with identification of positive serum anti-Hu antibodies and a mediastinal seminoma. The patient was treated with immunotherapy including steroids, IVIG, azathioprine, rituximab and plasmapheresis as well as mediastinal lesion resection. However, he continued to experience EPC, psychomotor impairment along with left hemiparesis and dysarthria. Given clinical progression with failure to respond to immunotherapy and anti-seizure polytherapy, hemispherotomy was attempted and seizure freedom achieved. A review of the literature found only sixteen cases of neurological presentations associated with anti-Hu antibodies in children, confirming the rarity of EPC in these cases. Thus, this report provides a new observation of germ cell mediastinal tumour associated with anti-Hu antibodies in children broadening the spectrum of anti-Hu–associated neurologic disorder in children and highlighting the importance of considering antineuronal antibody testing in children presenting with EPC and brain lesions suggestive of Rasmussen encephalitis.