A Case of Autoimmune Encephalitis in Disguise in an Adolescent Female

Introduction: Autoimmune encephalitis is a frequent cause of encephalopathy in children. It has wide spectrum of clinical presentations. Establishing a diagnosis can sometimes be challenging as it comes with certain degree of uncertainty. Timely diagnosis and effective intervention are prudent to prevent further progression of neurological dysfunction.

Case Description: We report a 15-year-old female previously healthy with new onset of fever, increasing somnolence, and altered mental status requiring intubation at a local emergency room. On obtaining more information, patient approximately 2 weeks prior, started having manic behavior, grandiose delusions, and sleep disturbances. She was started on Trazodone 25 mg at night and referred to a child psychiatry clinic. Symptoms worsened and patient developed motor tics for which she was started on Olanzapine 2.5 mg twice daily. Due to lack of improvement, Olanzapine dose was increased to 5 mg. Furthermore, patient was transferred to another behavioral health care facility where she was started on Lithium, Droperidol for presumed bipolar disorder, and Benzatropine for presumed extrapyramidal symptoms. Patient upon presentation, had hyperthermia, dry skin, minimal response to deep stimuli, pupils were 3 mm, equal and reactive to light, brisk deep tendon reflexes with clonus and rigidity. Diagnosis of encephalitis due to infectious or autoimmune etiology, and serotonergic syndrome were considered. Her laboratory workup was remarkable for creatinine kinase (CK) of 1615 U/L and creatinine (Cr) of 0.8 mg/dL. Brain CT and MRI were nonrevealing, and urine toxicology studies were negative. Continuous electroencephalogram (EEG) ruled out nonconvulsive status epilepticus. Cerebrospinal fluid analysis revealed protein 30 mg/dl, glucose of 72 mg/dl, IgG 11.6 mg/dl, negative viral encephalitis panel, oligoclonal bands 32, and N-methyl-D-aspartate (NMDA) receptor antibody 1:160. Diagnosis of autoimmune encephalitis was made. She was started on 0.5 mg/kg/day IVIG for 4 days, 1000 mg/day intravenous methylprednisolone for 3 days, two Rituximab infusions, and therapeutic plasma exchange on every other day for 5 cycles. CT abdomen ruled out paraneoplastic phenomenon secondary to ovarian tumors. As her sensorium improved partially, she was extubated to room air. During intensive care unit stay, she developed significant autonomic dysregulation and orofacial dyskinesia that improved with Propranolol and Clonidine. Patient was subsequently transferred for rehabilitation services.

Discussion: Diagnosis and management of autoimmune encephalitis can present a challenge with the wide spectrum of symptoms described in literature. It’s crucial to consider the diagnosis of autoimmune encephalitis in the setting of acute neurological, cognitive, and psychiatric symptoms. Furthermore, clinical picture can be clouded when anti-psychotic medications are started as alternative diagnoses are being entertained.

Conclusion: Autoimmune encephalitis is a challenging diagnosis and should be considered in any child with acute or subacute encephalopathy. Degree of neurological dysfunction can be severe and with disabling long-term outcomes. High index of suspicion can guide early diagnosis and intervention.