A 19-Month-Old Spanish Boy with Anti-NMDAR Encephalitis: Case Report and Review of Literature

Background and Aim: The classic definition of acute encephalitis consists of altered consciousness associated with fever, seizures or focal neurological alterations on neuroimaging or electroencephalography. However, there are particularities that may provide a glimpse of the probably autoimmune versus infectious etiology of the same neurological picture. Case presentation: A 19-month-old male starts with motor clumsiness and refusal to ambulation and leg claudication in the context of febrile pharyngotonsillitis. Simultaneously, first episode of forced gaze’s lateralization and cephalic deviation with right tonic movements and sucking. On examination: intense irritability with no contact, denial-type stereotypies, hemiparetic gait, pronation and adduction of the right arm and foot with frequent stumbling. Results: Neuroimaging tests, electroencephalogram, laboratory tests and antistreptolysin-O were normal, no pathological clinical exome and detection of antibodies in cerebrospinal fluid paired with serum. Such as diagnosis: acute autoimmune encephalitis due to anti-NMDA-R (N-methyl-D-aspartate Receptor) antibodies and movement disorder (choreoathetosis, hemidystonia). We initiate treatment with intramuscular penicillin and oral clobazam with erratic response. Fortunately, high doses of intravenous (iv) corticosteroids and immunoglobulins, oral corticotherapy and iv rituximab on our patient were used. Months later, clear improvement with autonomous ambulation without assistance, adequate manual opening and entire disappearance of dystonic-myoclonic movements. Conclusions: Choreoathetoid movements accompanied by irritability in an infectious context should lead us to think of Sydenham's chorea. However, new developments in the analysis of biological samples and a high index of suspicion may lead us to autoimmune pathology and the consequent early use of immunotherapy with optimal results.