Hypertrophic Pachymeningitis in an Individual with Microscopic Polyangiitis

Abstract

Hypertrophic pachymeningitis (HPM) is a rare disorder that thickens the dura mater, occurring in association with trauma, infection, neoplasm, and autoimmune disease.1 In autoimmune diseases, HPM may occur with various conditions, including myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA)-positive vasculitis.1, 2 A case of visual loss due to HPM during a course of MPO-ANCA-positive microscopic polyangiitis (MPA) is presented. A 70-year-old woman who had been diagnosed with renal biopsy-proven MPA was admitted to the hospital because of frontal headache and right visual impairment. She had no history of bronchial asthma, sinusitis, or eosinophilia. On admission, right uncorrected vision decreased from 20/28.5 to 20/500. Laboratory examination revealed white blood cell count of 11,940/μL, red blood cells 402 × 104/μL, platelets 25.1 × 104/μL, aspartate aminotransferase 16U/mL, alanine aminotransferase 20 U/mL, lactate dehydrogenase 242 U/mL, alkaline phosphatase 133 U/mL, gamma-glutamyl transpeptidase 26 U/mL, serum creatinine 1.2 mg/dL, C-reactive protein 1.1 mg/mL, erythrocyte sedimentation rate 56 mm/h, CH50 45 U/mL, C3 147.0 U/mL, C4 37.0 U/mL. MPO-ANCA was 23 U/mL (normal range <10 U/mL), whereas proteinase-3-ANCA was negative. Examination of cerebrospinal fluid indicated lymphocytic pleocytosis without evidence of infectious organisms, including syphilis, tuberculosis, and fungi. Axial T1-weighted gadolinium-enhanced cranial magnetic resonance imaging (MRI) showed diffuse thickening and enhancement of dura mater around the frontal cranial dura, consistent with HPM (Figure 1A). The woman was diagnosed with HPM associated with MPO-ANCA-positive MPA. She was treated with methylprednisolone 500 mg/d for 3 days, followed by prednisolone 50 mg/d. Headache improved, and visual activity improved to 20/200, and MPO-ANCA titers returned to a normal range. MRI findings of dura mater after the treatment also improved (Figure 1B). HPM is pathologically characterized by infiltrations of lymphocytes and plasma cells into the dura mater. HPM may occur in association with underlying disorders such as infection, malignancy, and autoimmune disease.1 Most recently, immunoglobulin G4–related disease was reported to induce HPM.3 In cases of autoimmune diseases, granulomatosis with polyangiitis (Wegener's) is the autoimmune disease most likely to cause HPM. Even in cases with granulomatosis with polyangiitis (Wegener's) that is usually a positive for proteinase 3-ANCA, MPO-ANCA is frequently positive when complicated with HPM.4, 5 Thus, a positive MPO-ANCA is reported to be closely associated with HPM.5 MPA, a disease that is most closely associated with MPO-ANCA, has rarely been reported in a setting of HPM, only three cases having been reported of MPA associated with HPM.6-8 An additional case of MPA complicating HPM is reported herein. This case also had visual disturbance. Central nervous system involvement is infrequent in MPA. Optic neuropathy was reported to occur in individuals with HPM.9 HPM should also be a concern in individuals with visual disturbance with MPA. ANCA-associated vasculitides, including MPA, are increasingly recognized in elderly adults, with a median age of 65 in one study,10 but HPM in individauls with MPA had been rarely reported. The oldest reported case of HPM with MPA was in an 81-year-old individual.8 The 70-year-old woman reported herein is the second oldest case of MPA complicated with HPM. Because the incidence of MPA is greatest in elderly adults, HPM should be considered when neurological manifestations, including visual disturbance, occur during a course of MPA. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Tsuda, Shinoda, Hounoki: case management. Taki: initial assessment and management of the case, study concept and design, preparation of manuscript. Tobe: literature review. Sponsor's Role: None.