Objective:

N/A

Background:

Powassan virus is a tickborne Flavivirus that can cause neuroinvasive disease with high morbidity and mortality. Symptoms often begin with flu-like illness and can progress to encephalitis, respiratory failure, coma, or death. Cerebrospinal fluid (CSF) typically shows pleocytosis and elevated protein. MRI findings may include T2/FLAIR signal intensity in the basal ganglia, thalamus, and brainstem. We present an atypical case of Powassan virus encephalitis with non-inflammatory CSF findings.

Design/Methods:

Case report

Results:

A 68-year-old female with chronic small lymphocytic lymphoma on ibrutinib, prior Lyme disease, and Babesiosis, presented with weakness, fever, and confusion, following a tick bite one week prior. She had leukopenia, thrombocytopenia, and lactic acidosis. Initial workup including lyme, babesia and anaplasma, was negative. Ibrutinib was stopped, and empiric antibiotics and antivirals were started while awaiting lumbar puncture (LP) results. Initial LP revealed 1 RBC, 1 nucleated cell, glucose 59 mg/dl, and protein 105 mg/dL. Serum and CSF infectious and neurologic tests, including West Nile, JCV/BK virus, HSV, VZV, Eastern Equine Encephalitis, St. Louis Encephalitis, California encephalitis, Western Equine Encephalitis, were negative. MRI showed patchy FLAIR hyperintensities in the right caudate head, hypothalamus, thalami, and cerebellum, without leptomeningeal enhancement. EEG showed triphasic waves with background reactivity. Her condition deteriorated, requiring intubation and she became comatose. Repeat LP 8 days after initial, showed normal protein and glucose, 14 nucleated cells, and 94% lymphocytes. Initial state lab serum Powassan virus testing was inconclusive, later returned presumptive positive, with CDC serum positive at 1:10 (CSF <1:2). Despite improvement in MRI lesions, her mental status remained poor, requiring tracheostomy and PEG tube placement.

Conclusions:

Powassan virus encephalitis is a rare, severe arboviral infection with increasing incidence, particularly in immunocompromised patients with tick exposure. This case is unique due to the non-inflammatory CSF findings, documented only twice before to the best of our knowledge.