Anti-N-methyl-D-aspartate (Anti-NMDA) Receptor Encephalitis – A Synopsis
Anti- N-methyl-D-aspartate (NMDA) receptor encephalitis is a fascinating disorder that was first described in 2007. Initially thought to be exclusively a paraneoplastic disorder occurring in young females with an ovarian teratoma, it is now recognised that this syndrome can occur in children and adults with or without a tumour. 
The disorder has garnered media attention after the book by Susannah Cahalan, Brain on Fire, which was made into a movie.
According to the Dalmau, one of the authors of the original publication describing Anti-NMDAR encephalitis  –
In my experience, the answer started to be revealed in December 2003 after we saw a young woman with encephalitis of unknown cause who had been in the Intensive Care Unit for several weeks. She was brought to the hospital for the acute onset of change in behaviour and prominent psychiatric symptoms that progressed rapidly to unconsciousness and central hypoventilation. All diagnostic investigations had been negative except for the presence of a small ovarian teratoma that was believed to be unrelated to her disease and owing to her poor clinical condition, it was not removed. She was given empiric immunotherapy and eventually recovered.
The trial of encephalitis with prominent psychiatric symptoms and hypoventilation in a young woman with an ovarian teratoma and the recovery with immunotherapy were crucial in linking a clinical picture to that of another three young women with an identical syndrome who also had ovarian teratomas.
Despite the remarkable syndrome resemblance amongst the four patients and their clinical and CSF features suggesting an immune-mediated encephalitis, their serum and CSF were negative for all neuronal antibodies known at the time.
It took six months to optimise the tissue processing until it showed a unique pattern of neuropil reactivity with the patient samples. The identity of the antigen (NMDA receptor R was obtained two years later). Nowadays the entire discovery process would just take a few weeks. (Dalmau, 2016)
As Anti -NMDAR encephalitis is a relatively recent discovery, there is often a delay in diagnosis because of the lack of knowledge and clinical experience about the disorder.
Furthermore, the presence of pronounced psychiatric symptoms can often result in a misdiagnosis of functional psychosis or schizophrenia.
Lennox BR, Palmer-Cooper EC, Pollack T, et al. (2017) Prevalence and clinical characteristics of serum neuronal cell surface antibodies in
first-episode psychosis: A case-control study. Lancet Psychiatry 4: 42–48.