BK virus encephalitis in an immunocompetent patient

Objectives: To describe a previously healthy patient now suffering from monophasic encephalitis caused by a primary infection with BK virus and to discuss possible risk factors for developing BK virus encephalitis. Design: Case report. Setting: Referral hospital. Patient: The patient was examined on referral. Main Outcome Measures: The main diagnostic tests performed were serology, polymerase chain reaction on cerebrospinal fluid samples, and cranial magnetic resonance imaging. Results: During the course of the patient's encephalitis, an IgM titer developed against polyomavirus, followed by anti-polyomavirus IgG. Wild-type BK virus was demonstrated in cerebrospinal fluid samples. Cranial magnetic resonance imaging showed diffuse reversible white matter changes most prominent on T-2-weighted images. Conclusion: We conclude that diagnostic tests for BK, a human polyomavirus, should be included in the screening program for encephalitogenic pathogens.