Severe late-onset neutropenia induced by ocrelizumab in a multiple sclerosis patient: A case report.

Ocrelizumab is a recombinant humanized antibody targeted against CD-20 molecule, which was approved for the treatment of relapsing and primary progressive multiple sclerosis. Common adverse events of ocrelizumab include infusion-related reactions like rash, pruritus, and flushing. Late-onset neutropenia (LON) is a rarely reported complication of ocrelizumab therapy. We report a case of severe late-onset neutropenia in a patient with primary progressive multiple sclerosis treated with ocrelizumab with neutropenia occurring 3 months after the last dose received treated with empirical broad-spectrum intravenous antibiotics and filgrastim. Severe late-onset neutropenia is a rare unpredictable adverse event and outlines the importance of regular routine blood workup for detecting severe neutropenia early in its course.