Presentation of Neurological Rosai-Dorfman Disease Over 12 Years: A Case Report.

Rosai-Dorfman disease (RDD) is a rare, non-Langerhans cell histiocytosis that classically presents with cervical lymphadenopathy. Neurological involvement occurs in less than 5% of cases and is often associated with extra-axial lesions. Diagnosis of RDD in the setting of neurological deficits is challenging, as RDD often mimics meningioma and neurosarcoidosis on neuroimaging. Herein, we describe a case report of a 50-year-old African American man who was previously treated with radiation for presumed meningioma of the brainstem 12 years prior to the current presentation. The brainstem lesion progressed to include the pachymeninges despite radiation, and the patient developed papilledema and involvement of the bilateral cochlea. Lack of response to radiation, involvement of the pachymeninges, and development of papilledema and bilateral hearing loss led to an updated diagnosis of neurosarcoidosis. On current presentation, the patient was brought to the emergency department for altered mental status, seizures, and left-sided hemiparesis. Initial workup was negative for stroke, meningitis, and toxic or metabolic encephalopathies. Long-term electroencephalography confirmed seizures originating from the right frontal lobe, which was controlled with antiseizure medications. Magnetic resonance imaging revealed worsening diffuse brainstem and pachymeningeal enhancement of the bilateral cerebral convexities, suggesting progression of the disease. Workup for systemic malignancy revealed a hypodense soft tissue mass encasing the left kidney, raising concern for metastatic disease. Biopsy of the meninges and the renal mass confirmed RDD with multiorgan involvement. Diagnosis of RDD in this patient marks the longest duration from onset to diagnosis ever reported, indicating the need for tissue diagnostics in uncertain cases.