Case Presentation: A 4-year-old presented with persistent fever, headache and vomiting. History was significant for a 5 day febrile illness 1 month earlier and a family history positive for late-onset rheumatoid arthritis in a maternal grandparent. Parents reported that 4 days following resolution of the illness, his fever (up to 104F) recurred and persisted daily for 3 weeks despite use of ibuprofen. He grew lethargic with poor appetite and stopped ambulating. His pediatrician referred him to the emergency department where he was diagnosed and treated for sinusitis. In clinic the next day, he remained febrile and appeared uncomfortable but without neck stiffness or other focal neurologic signs. Laboratory studies showed a leukocytosis, mildly elevated C-reactive and elevated sedimentation rate but were otherwise unremarkable. Flow cytometry was also normal. He worsened clinically with development of non-bilious non-bloody emesis, urinary incontinence and altered mental status. Upon admission, he was very irritable concerning for meningitis and an extensive infectious workup was initiated, lumbar puncture performed, and empiric antibiotics started. Cerebral spinal fluid (CSF) opening pressure was elevated at 36 cmH2O and pleocytosis was noted. On funduscopic exam, bilateral papilledema was present. Imaging was unremarkable. He developed visual loss on the left and was taken urgently to the operating room for lumbar drain placement and additional brain imaging. CSF opening pressure had increased to 55 cmH2O and magnetic resonance imaging (MRI) revealed patchy areas of enhancement in the white matter suggestive of encephalitis or demyelinating disease. Electroencephalography was normal and cerebral angiogram showed no evidence of CNS vasculitis. Infectious versus autoimmune etiology remained high on the differential. He was treated with high dose corticosteroids and a 5 day course of intravenous immunoglobulins. He showed rapid clinical improvement and was discharged on hospital day 10. Post-discharge, specialized autoimmune analysis of the CSF was positive for MOG-IgG antibodies 1:10000 titer and a final diagnosis of MOG antibody-positive encephalitis was made. On exam 4 weeks later, vision was intact, visual fields were full to confrontation, sharp discs were seen on fundoscopic exam, he was ambulating again and overall returned to baseline.
Discussion: Myelin oligodendrocyte glycoprotein (MOG) has been identified as an antibody marker seen in children with acute disseminated encephalomyelitis, neuromyelitis optica spectrum disorder and relapsing optic neuritis, it is increasingly being implicated in other demyelinating conditions. While MOG-IgG Encephalitis has been described, it is a rare condition. Knowledge about this disorder has expanded due increased availability of serum biomarkers assays. Here we describe a case of MOG-Antibody positive Encephalitis in a child with family history of autoimmune disease and subacute onset of illness. This case reminds clinicians of the importance of keeping a broad differential, considering and testing for autoimmune etiology.
Conclusions: Children presenting with encephalitis that cannot otherwise be attributed to an infectious etiology should be tested for MOG-IgG Antibody as part of a complete rheumatologic workup where autoimmune encephalopathy is a possibility. A high suspicion for this disorder and prompt treatment can reduce the severity of neurological sequelae.