Antibody Negative West Nile Virus Encephalitis in a Patient on Anti-CD20 Therapy for Multiple Sclerosis
Background:
West Nile Virus is a single-stranded RNA virus commonly transmitted to humans by mosquitoes. Most often, it causes what is called West Nile Fever characterized by constitutional symptoms including fever, headache, nausea, vomiting and rash. Less commonly, the West Nile Virus manifests as encephalitis. Immunocompromised patients are especially susceptible to this complication.
Results:
A 47-year-old woman with RRMS on ocrelizumab and a previously resected right temporal lobe AVM was admitted with several days of fever, confusion and falls in the setting of several months of worsening tremor and gait instability. On exam, she was lethargic, inattentive and poorly responsive to requests. She had intermittent left hemispatial neglect, fluctuating left hemiparesis with fixed paraparesis, and variable tremors. Initial CT head showed a 1 cc left caudate hemorrhage. MRI Brain with and without contrast showed encephalomalacia from her prior AVM resection, stigmata of longstanding RRMS, a subacute L caudate hemorrhage, but no contrast enhancement. CSF had 100 WBCs with a lymphocytic predominance and a protein of 41. The Biofire Meningitis/Encephalitis panel was negative for all tested organisms. Antibiotics for bacterial meningitis were deescalated, but she received IV acyclovir for 10 days. During that time, she remained encephalopathic and intermittently febrile. EEG did not show any seizure or epileptiform discharges. Eventually, a NYS DOH Encephalitis panel returned PCR positive for West Nile Virus. A previous IgM/IgG test for WNV from the same CSF sample was negative. The patient was started on IVIG and remdesivir. There was initially some improvement in her mentation, but after completing therapy, her exam has remained the same.
Conclusions:
Patients on B-cell depleting therapies are susceptible to neuroinvasive pathogens. Their workup should take into consideration that there may not be an antibody response to these pathogens. Additional medication therapies should be considered even if the care is usually supportive.
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