BK virus assessment in lupus nephritis: is this a potential trigger for disease activity?

Objective: The BK virus (BKV) is a human polyomavirus widely distributed in the population. In deeply immunosuppressed patients, such as those undergoing renal transplantation, the virus can be reactivated, leading to BKV nephropathy; the main risk factor is the degree of immunosuppression. Limited literature analyzes BKV infection in lupus nephritis (LN). Our objective was to study the BKV in LN. Material and methods: Patients over 18 years with LN confirmed by histology were prospectively studied for 1 year at the University Hospital. BKV viremia was detected and quantified using real-time-polymerase chain reaction. Results: Twenty-seven patients were included, 85% were women. About 100% were perceived as Caucasians. The 77.8% had proliferative LN at the debut, and the median evolution time was 11.5 years (IQR: 4.0-16.8). At enrollment, all patients received immunosuppressive treatment with prednisone (62%), mycophenolate (85%), and/or hydroxychloroquine (89%). We did not obtain positive viremia in any patient. At the time of blood sampling, 100% were in remission, and of them, 89% were in complete remission. Conclusions: We did not detect any patients with positive BKV viremia. The absence of viremia could be due to the high degree of remission and low immunosuppressive burden in this population.