Is low threshold of B cells an obligatory monitoring indicator of repeated RTX infusion in the treatment of Neuromyelitis Optica spectrum disorder? – A report of two cases

Abstract Background B-cell subset in the peripheral blood is widely recognized as a monitoring indicator of repeated rituximab (RTX) infusion timing in clinical studies of Neuromyelitis Optica Spectrum Disorder (NMOSD). However, its threshold is undetermined and may vary individually. Case presentation We report two cases of NMOSD treated with low-dose RTX with long-term follow-up. In the two cases, the patients kept relapse-free status in most of the time points with pre-specified repeated RTX infusions, no matter the percentage of total B cell (CD19+) was above 1%, or memory B-cell (CD19+CD27+) was above 0.05% in the initial two years and 0.1% thereafter, as previously proposed in most of studies. Conclusions The two cases raise the question whether the level of B-cell is an indicator for repeated RTX infusion. Re-defining optimal indicators for repeated RTX infusion in NMOSD will be meaningful for reducing potential long-term adverse reactions of this treatment, as well as gaining a more cost-effective result.