Abstract
BACKGROUND: Ocrelizumab is an anti-CD20 monoclonal antibody that has been shown to reduce disability progression in primary progressive multiple sclerosis (MS). The adverse event profile is still being determined through postmarketing surveillance and case reports. OBJECTIVE: To report a case of severe late-onset neutropenia associated with ocrelizumab in a patient with primary progressive MS. METHODS: Case report. RESULT: A 34-year-old male with primary progressive MS developed severe late-onset neutropenia 42 days after infusion of ocrelizumab, which necessitated hospital admission and administration of broad-spectrum antibiotics and granulocyte colony-stimulating factor. CONCLUSION: Late-onset neutropenia is a rare complication of ocrelizumab. Patients should be counseled to present for urgent evaluation if they develop fever.