Anti-N-methyl-D-Aspartate-Receptor encephalitis following herpes simplex virus encephalitis - Presenting as a pediatric patient with abnormal movements and psychiatric manifestation

Herpes simplex virus (HSV) encephalitis remains one of the more severe forms of childhood encephalitis. The clinical course of HSV encephalitis is usually monophasic but occasionally complicated by a clinical relapse, causing biphasic illness. Sometimes relapse may be due to secondary immune mechanisms. Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis is an example of immune-mediated relapse following herpes encephalitis. This is still underrecognized, with probable grave consequences if not treated early. Our index case was an 8-year-old male child with severe generalized choreoathetosis and behavioral disturbances, presented 4 weeks after documented HSV encephalitis. Cerebrospinal fluid (CSF) was positive for anti-NMDA receptor antibodies. The diagnosis was confirmed and treated with intravenous (IV) immunoglobulins (2 g/kg) and IV pulse-dose methylprednisolone (30 mg/kg) for 5 days. Other supportive management included tablet revocon 25 mg (tetrabenazine) 1/4 tablet BD, clonazepam 0.25 mg one tablet BD, and syrup sizodon (risperidone) 0.5 mg BD. The patient is on regular follow-up and is recovering well but slowly. Patients with relapsing symptoms following HSV encephalitis or prolonged atypical symptoms, with repeat CSF-negative polymerase chain reaction for HSV should routinely be tested for NMDA receptor immunoglobulin G antibodies in CSF and/or serum. It is important to be aware of this differential diagnosis because patients respond well to immunotherapy.