Are We Missing Subtle Forms of Anti-N-Methyl-D-Aspartate Encephalitis With the Current Diagnostic Approach? A Case Report

Encephalitis related to antibodies against the N-methyl-D-aspartate receptor (NMDAr) is a recently described clinical entity in which IgG autoantibodies against the NR1 subunit of the NMDAr lead to the appearance of complex neuropsychiatric symptoms. As psychiatric symptoms predominate in early stages, anti-NMDAr encephalitis is frequently mistaken as a primary psychiatric disorder which delays treatment and has serious consequences for patients. This report presents the case of a 24-year-old woman with a subacute onset of psychotic and catatonic symptoms in whom current diagnostic criteria for probable anti-NMDAr encephalitis were not fulfilled. On the basis of the red flags that have been proposed to raise suspicion of anti-NMDAr encephalitis, a study of fluorodeoxyglucose positron emission tomography was requested and demonstrated bilateral occipital hypometabolism consistent with clinical suspicion of anti-NMDAr encephalitis. Once the appropriate treatment was established, the patient recovered completely. This case supports the need to maintain clinical suspicion of anti-NMDAr encephalitis, even when conventional diagnostic tests have been normal. Psychiatrists should be familiar with this entity to promote timely diagnosis and prompt treatment.