Late-onset neutropenia and neurological relapse, during long-term rituximab therapy in myelin oligodendrocyte glycoprotein-antibody spectrum disorder.

Late-onset neutropenia after rituximab therapy (LONART) is defined as a fall in the absolute neutrophil count below 500/mm3 at least 3 weeks after rituximab infusion, in the absence of any other explanation. LONART is rare during dysimmune conditions but can be life-threatening. We report on two patients with LONART and associated neurological relapse occurring in myelin oligodendrocyte glycoprotein (MOG)-antibody spectrum disorders. Rituximab was reintroduced in one patient, while the second patient was switched to tocilizumab. LONART can occur during anti-MOG spectrum disorders. Neurologists should be aware of this rare and treatable complication. Regular monitoring of blood cell counts is needed, and patients should be informed of the need to consult their physician if symptoms of infection appear.