[Steroid responsive chronic meningoencephalitis reminiscent of rheumatoid meningitis: a case report].

A 62-year-old woman presented at our hospital with a headache, cognitive decline, and fever that had persisted for 3 months. On admission, fever, headache, and mild cognitive dysfunction were all clearly evident, suggesting chronic meningoencephalitis. Laboratory examination showed mild neutrophilia as well as an increase in her erythrocyte sedimentation rate and serum C-reactive protein levels. MRI showed multiple small hyperintense lesions on T2 weighted image and diffusion weighted image (DWI) in the cerebral cortex and white matter. Contrast-enhanced T1 weighted image showed the abnormal pial enhancement along the cerebral sulci. Systemic evaluations for infectious organisms, autoantibodies, and malignant tumors were all negative. Her fever and neurological symptoms continued. As a result of worsening MRI findings, a brain biopsy was carried out. Neuropathological analysis revealed neutrophilic infiltration in the subarachnoid space and multinucleated giant cells. However, there was no vasculitis on the histological sections. This pathological finding was reminiscent of rheumatoid meningitis despite articular findings of rheumatoid arthritis, as well as rheumatoid factor (RF) and anti-CCP antibody tests being negative. After oral steroid therapy, her fever and inflammatory reactions by laboratory test diminished and her cognitive function improved remarkably.