Fever of Unknown Origin: An Unusual Presentation of Anti-N-Methyl-D-Aspartate Receptor Encephalitis

Anti-NMDA receptor encephalitis presenting as fever with undetermined cause

Autoimmune encephalitis is a rare disease which should be differentiated with aseptic encephalitis. Possessing anti-N-methyl-D-aspartate (NMDA) receptor autoantibody is the leading cause of autoimmune encephalitis. However, it may pose a diagnostic challenge to clinicians, especially non-psychiatric or non-neurologic specialist, resulting in a delayed initiation of treatment. Hence, we shared a case of anti-NMDA receptor encephalitis that got hospitalized at infectious diseases ward with the presentation of acute febrile illness that preceded characteristic neuropsychiatric symptoms.

Anti-N-Methyl-D-aspartate receptor encephalitis masquerading as fever of unknown origin

Fever of unknown origin (FUO) is a diagnostic challenge. Anti-N-methyl-D-aspartate receptor encephalitis should be considered in children with FUO and new-onset neurological symptoms without significant encephalopathy.

Aetiology of pyrexia of unknown origin in north India

The aetiology of pyrexia of unknown origin (PUO) varies dramatically according to epidemiology. We studied the cause and spectrum of PUO in Indian adults. A total of 152 patients (112 prospectively and 40 retrospectively) met Petersdorf and Beeson's criteria. The diagnostic evaluation was guided by potentially diagnostic clues, based on a 'step-wise' approach. The five main categories, i.e. infectious, neoplastic, non-infectious inflammatory, miscellaneous and undiagnosed comprised 43.4%, 21.5%, 19.7%, 2.0% and 12.5%, respectively. The top three causes were tuberculosis (n = 43, 28.3%), lymphoma (n = 19, 12.5%) and adult-onset Still's disease (n = 12, 7.9%). Tuberculosis predominated in all age groups, and about 70% of cases had the extrapulmonary form, the most common being gastrointestinal. Hodgkin and non-Hodgkin lymphomas were equally distributed, but solid malignancies were uncommon. Adult-onset Still's disease was the second commonest cause in adults aged ≤ 40 years. Fever resolved spontaneously in 12/19 cases of undiagnosed cause. Extrapulmonary tuberculosis remains the most prevalent PUO in India.

Catatonia in N-methyl-d-aspartate receptor antibody encephalitis: Phenomenological characteristics from a systematic review of case reports

OBJECTIVE

To ascertain the phenomenological characterisation of catatonia in N-methyl-d-aspartate receptor antibody encephalitis (NMDAr-AbE).

METHODS

A systematic review of case reports was undertaken in accordance with PRISMA guidelines. Case reports of NMDAr-AbE containing sufficient information on the cases' clinical presentation and meeting the study's inclusion criteria were selected. Cases were searched for clinical data in keeping with core catatonic signs by applying the screening instrument of the Bush-Francis Catatonia Rating Scale. When two or more core signs were ascertained catatonia was considered to be present.

RESULTS

2645 records were identified through the database search. Following screening and application of eligibility/inclusion criteria 139 articles were selected reporting on 189 individual subjects. Catatonia was present in 60% of these cases. The most prevalent signs were immobility/stupor (70%), mutism (67%), excitement (50%), posturing/catalepsy (34%), stereotypies (31%), and rigidity (30%). Immobility/stupor and excitement co-occurred in the same patient in 33% of cases.

CONCLUSION

The phenomenological profile of catatonia in this sample of cases of NMDAr-AbE was characterised by a preponderance of signs in the hypokinetic spectrum. However, excitement often co-occurred in these patients suggesting that fluctuations in catatonic semiology may be frequent.

Anti-NMDA Receptor Encephalitis: Clinical Features and Basic Mechanisms

In slightly more than 10 years, anti-NMDA receptor (NMDAR) encephalitis has changed from a rare paraneoplastic syndrome to the most common cause of nonviral encephalitis. It presents fulminantly with progressive psychosis, seizures, and autonomic dysfunction, leading to death if untreated. However, rapid recognition and treatment can lead to survival and a return to baseline levels of functioning in many patients. While initially associated with ovarian teratomas, it is now associated with other tumors and can reflect a postviral event. The antibodies to the NMDAR made in this syndrome are pathogenic and are directed at the extracellular domain of the GluN1 subunit. Such antibodies lead to internalization of NMDARs in model systems, leading to a physiological state characterized by NMDAR hypofunction. Analogous disorders, characterized by antibodies to other synaptic receptors, present with neurological and psychiatric dysfunction and also appear to reflect antibody-induced internalization of receptors. However, this simple pathophysiology may be too simplistic to reflect the complexity of events in anti-NMDAR encephalitis. Future scientific investigations may allow a more complete understanding of this disorder and improve treatment of anti-NMDAR encephalitis.