Dramatic efficacy of ofatumumab in refractory pediatric-onset AQP4-IgG neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is a rare but severe demyelinating condition that affects mainly adult patients. However, childhood onset has been reported and is related to a very active disease1 and poor outcome. Several evidence suggest that the crucial role of antiaquaporin-4 (AQP4) antibodies (Abs) in the pathogenesis of NMOSD justify the use of plasma exchanges and rituximab (RTX) as a treatment strategy targeting Ab and B-cells, respectively. Although RTX, a chimeric anti-CD20 monoclonal Ab, is associated with great efficacy in preventing NMOSD relapse, its use can be limited by severe infusion-related adverse event and infectious risk. Ofatumumab (OFA), a fully humanized anti-CD20 monoclonal antibody, has shown some efficacy in dysimmune diseases, including multiple sclerosis (MS).2 In pediatrics, OFA has been used in RTX-resistant nephrotic syndrome.3 We report here the case of a young girl with a very active AQP4-Ab NMOSD, with clinical worsening despite intensive immunosuppressant therapies. The use of OFA was associated to dramatic efficacy and great safety.