Early relapse after RTX initiation in a patient with NMO/MS overlap syndrome: How long to conclude to a failure treatment?

We report a dramatic clinical and radiological worsening within two months after rituximab initiation in a patient with NeuroMyelitis Optica/Multiple Sclerosis (NMO/MS) overlap syndrome. Case study. A 45-year-old Caucasian woman with NMO/MS overlap syndrome experienced a severe myelitis nine weeks after first rituximab infusion, with extensive new gadolinium-enhanced spinal cord lesions. This case report illustrates the limits of MS and NMO-Spectrum Disorder classification and challenges the criteria of therapeutic failure within the 6 months after rituximab initiation. •limits of MS and NMO-Spectrum Disorder classification.•challenge of the criteria of therapeutic failure within the 6 months after rituximab initiation.•possible early exacerbation of CNS inflammatory disease after rituximab onset.