Hypertrophic Pachymeningitis with Characteristics of Both IgG4-related Disorders and Granulomatosis with Polyangiitis.

We herein report a 73-year-old man with isolated hypertrophic pachymeningitis (HP) showing serological and pathological characteristics of both IgG4-related disorders and granulomatosis with polyangiitis. The patient presented with chronic onset headaches and ophthalmalgia. Brain magnetic resonance imaging (MRI) revealed a hypertrophic enhanced dura mater. Serum IgG4 and myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA) levels were elevated. A dura mater biopsy showed infiltration of numerous IgG4-positive plasma cells and granulomatous inflammation without apparent vasculitic lesions, storiform fibrosis, or obstructive phlebitis. Corticosteroid treatments improved his clinical symptoms and MRI findings. There have been reports of MPO-ANCA-positive IgG4-related HP presenting as granulomatous inflammation in the dura mater.