Effect of mycophenolate mofetil on the white blood cell count and the frequency of infection in systemic lupus erythematosus

Leukopenia is a common manifestation of SLE. Addition of immunosuppressive therapy in a SLE patient who is already leukopenic is a clinical concern. It could worsen leukopenia, increase the risk of infection, or both. The aim of this study was to analyze the immediate effect of mycophenolate mofetil on the white blood cell count and the rate of infection in SLE patients. Two hundred and forty-four patients within the Hopkins Lupus Cohort who were newly started on mycophenolate mofetil were included in the study. The white blood cell count and interval infection history on the day mycophenolate mofetil was started were compared with the white blood cell count and interval infection history at the next visit. The study was based on 244 patients who began taking mycophenolate mofetil in the cohort. The study population included 47 % African Americans, 44 % Caucasians, and 9 % other ethnicities. There was a slight but not statistically significant increase in the white blood cell count (6.63 vs. 7.01), after starting mycophenolate mofetil. Patients with a baseline white blood cell count <3000/mm³ did have a statistically significant increase in the white blood cell count after starting mycophenolate mofetil (2.57 vs. 5.13, P = 0.0047). We also found a statistically significant increase in the risk of bacterial infection (but not viral infection) after starting mycophenolate mofetil (4 vs. 9 %, P = 0.0036). Leukopenia does not worsen with mycophenolate mofetil. However, mycophenolate mofetil appears to slightly increase the rate of bacterial (but not viral) infection.