Successful Treatment with Rituximab in a Patient with Clinically Suspected Small-vessel Primary Central Nervous System Vasculitis Refractory to Cyclophosphamide Pulse Therapy.

A 58-year-old man developed a progressive cognitive impairment and recurrent cerebral infarctions that were refractory to antithrombotic therapy. No abnormalities were detected in the major cerebral arteries, and a cerebrospinal fluid analysis revealed mild inflammatory findings. Although a brain biopsy was not feasible, the patient was clinically diagnosed with small-vessel primary central nervous system vasculitis based on comprehensive evaluations. Treatment with glucocorticoids and cyclophosphamide failed to prevent a relapse. The presence of cerebrospinal fluid oligoclonal bands and elevated interleukin-6 levels suggested intrathecal humoral or lymphocyte-mediated immune activity, and rituximab therapy led to clinical improvement. This clinical improvement indirectly suggests B-cell involvement, consistent with the efficacy of rituximab. Rituximab may therefore be an option for treating cyclophosphamide-resistant PCNSV.