Abstract
Background Ocrelizumab is an anti-CD20 recombinant humanized monoclonal antibody approved for the treatment of Relapsing Remitting Multiple Sclerosis (RRMS). Severe Late Onset Neutropenia (LON) is a serious, rare, and unpredictable complication of Ocrelizumab. LON is defined as an Absolute Neutrophil Count (ANC) of <1.5 X 109/L, developing >4 weeks after drug administration, preceded by a normal neutrophil count, and without another identifiable cause.
Method A case report of severe LON in a young Australian male on Ocrelizumab for the treatment of RRMS.
Results/Case Description We report a case of severe LON in a 36-year-old Australian male on Ocrelizumab for RRMS. Our patient presented with febrile neutropenic sepsis secondary to pneumonia complicating a viral upper respiratory tract illness 5 weeks following his 8th Ocrelizumab infusion (4 years of treatment). His Neutrophil count on presentation was <0.01 X 109/L. He was treated with Intravenous broad-spectrum antibiotics and the Granulocyte Colony Stimulating Factor (G-CSF) Filgastrim with rapid recovery. His neutrophils have remained normal since, including after a rechallenge with Ocrelizumab.
Conclusion Our case adds to the body of literature of Ocrelizumab-induced LON. It is important to be aware and vigilant of the severity and unpredictability of this complication, which is often associated with severe infections. Patients should be counselled regarding the importance of frequent blood monitoring, and early presentation to medical services when unwell. Whilst not all patients may develop LON upon rechallenging with Ocrelizumab, detailed discussions should be had with patients regarding the risks and benefits of continuing Ocrelizumab treatment.
