Introduction
Opsoclonus-myoclonus syndrome (OMS) associated with neuroblastoma (OMS-NB) is a refractory paraneoplastic syndrome presenting as opsoclonus, myoclonus, ataxia, dysarthria, behavioral and cognitive disorder. Although OMS-NB patients show good life prognosis [1], the neurological prognosis is poor. OMS-related neurological symptoms often remain even after tumor resection and inflict permanent neurological sequelae, including developmental, cognitive, and behavioral deficits, disturbing daily life in 30–70% of those patients. Some autoantibodies such as anti-glutamate receptor δ2 (GluRδ2) antibody and oligoclonal bands in cerebrospinal fluid (CSF) have been detected in OMS patients continuously, even after tumor resection.[2,3] Therefore, humoral autoimmunity has been considered the cause of OMS. Immunosuppressive therapies, including glucocorticoid and intravenous immunoglobulin (IVIg), have been reported as initial therapy[4], however pathogenesis-based treatment strategies have not yet been established.
We encountered a pediatric patient presenting with OMS-NB who showed an increased number of CD20-positive B cells in both CSF and neuroblastoma tissue. Unbiased B-cell receptor (BCR) repertoire analysis followed by next-generation sequencing revealed identical B-cell clone in both CSF and tumor tissue in our patient. This mechanism could facilitate the establishment of novel treatment strategies for OMS-NB.