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Teaching NeuroImages: Rosai-Dorfman disease presenting with progressive early-onset cerebellar ataxia

A 13-year-old girl presented with a 3-year history of progressive gait abnormality. She recently had a self-limited cervical lymphadenopathy. Neurologic examination showed brisk tendon reflexes and moderate ataxia. Brain MRI disclosed hyperintense lesions in the cerebellum and pons (figure, A). Spine MRI showed a heterogeneous lesion in the T12 vertebra (figure, B). Histopathology of the cervical lymph node confirmed Rosai-Dorfman disease (RDD) by showing emperipolesis (figure, C and D). The patient will be followed up in order to determine disease progression and therapy.