Thin hematoma and hypertrophic pachymeningitis related to otitis media with antineutrophil cytoplasmic antibody-associated vasculitis (OMAAV) along with rheumatoid meningitis: A case report.

We present the first case of hypertrophic pachymeningitis (HP) pathogenesis, where otitis media with anti-neutrophil cytoplasmic antibody-associated vasculitis (OMAAV) and rheumatoid meningitis (RM) caused severe inflammation, leading to the thin hematoma. The patient, a 64-year-old woman, had a daily right-sided headache without fever for two weeks and otitis media that was refractory to quinolone antibacterial drugs. Serum and cerebrospinal fluid showed a high titer of myeloperoxidase-specific ANCA, anti-citrullinated peptide (CCP) antibody along with a high anti-CCP antibody index score. On the gadolinium enhanced T1-weighted images, brain magnetic resonance imaging (MRI) revealed thickened dura mater in the right falx, fornix, cranial fossa, and tentorium. Leptomeningeal signs and inflammation of mastoid cavities were observed in gadolinium enhanced fluid-attenuated inversion recovery. Diffusion weighted imaging revealed patchy high intensity lesions in the right frontal subarachnoid space with interdural and subdural hematoma observed on susceptibility weighted imaging. Although a biopsy was not performed, we diagnosed HP caused by OMAAV and immediately started immunosuppressive therapy, which responded extremely well, based on the belief that the thin hematoma was caused by intense local inflammation due to the accompanying RM. Therefore, when diagnosing HP with focal hematoma by gadolinium-enhanced MRI and SWI, the possibility that the intense inflammation is caused by multiple pathologies such as OMAAV and RM should be considered.