Steroid-responsive chronic cerebellitis with positive glutamate receptor delta 2 antibody.

We report the clinical course of a 4-year-old girl with chronic cerebellitis (onset 2 days after diphtheria-pertussis-tetanus vaccination at 1 year and 7 months old) associated with anti-glutamate receptor delta 2 antibody, who improved dramatically with steroid therapy (methylprednisolone pulse therapy plus oral prednisolone). Recently, it has been reported that the anti-glutamate receptor delta 2 selectively expressed at the post-synaptic site of parallel fiber-Purkinje cell synapses has an important role in cerebellar function in the developing brain. The present case suggests that anti-glutamate receptor delta 2 antibody plays a primary role in an immune-mediated process causing chronic cerebellar symptoms, and the lesion site seems to be localized to the parallel fiber-Purkinje cell synapse. Because the cerebellum is strongly involved in language acquisition as well as motor development, treatment must facilitate time for language learning while reducing the side effects of the corticosteroid therapy.