Non-late-onset neutropaenia following treatment of multiple sclerosis with ocrelizumab

Late-onset neutropaenia is defined as an absolute neutrophil count of <1.5×10³cells/μL starting>4 weeks after the last dose of rituximab, in the absence of other identifiable causes. Late-onset neutropaenia is a rare adverse reaction to rituximab (observed in approximately 5% of patients). Rheumatic diseases constitute the main indication for rituximab; in these patients, neutropaenia appears after a mean of>28 days. Ocrelizumab is another monoclonal antibody that binds to CD20 (a glycosylated phosphoprotein mainly expressed on the membranes of B-lymphocytes); in January 2018, it was approved for the treatment of relapsing-remitting and primary progressive multiple sclerosis. We present a case of neutropaenia following intravenous infusion of ocrelizumab in a patient with primary progressive multiple sclerosis who presented with neutropaenic fever, herpetic stomatitis, and ecthyma gangrenosum only 20 days after infusion.