An unusual case of early onset opsoclonus-myoclonus syndrome: Case report and literature review

Opsoclonus-myoclonus syndrome is a rare neurological condition characterized by opsoclonus, myoclonus, ataxia, irritability, and sleep disturbances. In pediatric patients, symptoms usually start between 16 and 18 months of age; opsoclonus-myoclonus syndrome presentation in children under 6 months is rare. Approximately 50% of cases are associated with neuroblastoma. We report an early onset presentation of opsoclonus-myoclonus syndrome in a previously healthy, 3-month-old female infant. The diagnostic workup revealed no abnormalities. The patient underwent monthly cycles of dexamethasone pulses and intravenous immunoglobulin with a favorable response. After a few months, the patient presented intermittent opsoclonus before the next scheduled pulse so from the 9th cycle onwards, the intravenous immunoglobulin dose was increased to 2 g/kg. After 9 months of treatment, she was diagnosed with a latent Mycobacterium tuberculosis infection. Due to this infection, dexamethasone pulses were discontinued, and intravenous immunoglobulin treatment was maintained with clinical improvement The patient received 18 intravenous immunoglobulin cycles, leaving her with a score of one on the Mitchell-Pike scale. Developmental milestones have been attained according to age. Despite the range of therapeutic options for managing opsoclonus-myoclonus syndrome described in the literature, the efficacy of these available therapies needs to be better established. A modified upfront approach with dexamethasone and intravenous immunoglobulin could be an option in settings where rituximab is unavailable.