Immunologic and clinical responses to rituximab in a child with opsoclonus-myoclonus syndrome.

Opsoclonus-myoclonus syndrome (OMS) is an autoimmune disorder with serious neurodevelopmental morbidity and limited treatment options. We treated a toddler with moderately severe OMS with rituximab, a monoclonal anti-B cell antibody. The patient's clinical response was documented on videotape and scored with the OMS Evaluation Scale. Cerebrospinal fluid lymphocyte subsets were evaluated by flow-cytometric immunophenotyping, with a comprehensive panel of monoclonal antibodies. Eradication of cerebrospinal fluid B cells, which previously were expanded, was associated with dramatic clinical improvement. There also were secondary changes in other lymphocyte subsets that might be relevant to the clinical response and lack of serious infections. In addition to clarifying the immune response to B-cell depletion, these data reveal a promising new therapy for OMS that warrants a phase I clinical trial.