Delayed-onset flaccid paralysis related to west Nile virus reactivation following treatment with rituximab: a case report

BACKGROUND: Neurological manifestations of West Nile virus infection include meningitis, encephalitis and acute flaccid paralysis. Typically, West Nile virus-associated acute flaccid paralysis is characterized by acute and rapidly progressing limb weakness, occurring early in the course of the disease. CASE PRESENTATION: We report a patient of Yemenite descent who developed West Nile virus-encephalitis and poliomyelitis two weeks following treatment with rituximab for B cell lymphoma, and delayed encephalitis with ascending demyelinating polyneuropathy 6 months later. Diagnosis of the first episode was based on a high West Nile virus copy number in the blood polymerase chain reaction. During the second episode the patient developed encephalitis and flaccid asymmetric quadriparesis, accompanied by high IgM anti-West Nile virus titers in the blood and cerebrospinal fluid. CONCLUSION: The delayed polyneuropathy post-West Nile virus infection and encephalitis/poliomyelitis may be related to reactivation of the virus or to a delayed autoimmune (post-infectious) process, possibly accelerated by the recovering B-cell humoral immunity, 6 months after treatment with rituximab. This case depicts the complexities of the immune responses and their reconstitution following monoclonal antibody treatment and the diversity of neurological syndromes associated with West Nile virus infection.