IgG4-related hypertrophic pachymeningitis coexpressing antineutrophil cytoplasmic antibodies

IgG4 disease was first described in 2001 in a seminal paper by Hamano and colleagues: Syndrome of exocrine gland infiltration with associated raised serum IgG4 levels. IgG4 disease is manifested by the hallmark histopathologic features of lymphoplasmacytic infiltration of IgG4-positive plasma cells, storiform fibrosis, and obliterative phlebitis. Hypertrophic pachymeningitis (HP) has been increasingly recognized as a clinical manifestation of IgG4related disease (IgG4-RD) and is likely to account for a significant number of cases previously reported to be “idiopathic.” HP has been associated with alternate autoimmune disorders, specifically granulomatosis with polyangiitis (Wegner granulomatosis) with antineutrophil cytoplasmic antibody (ANCA) positivity. A subgroup of patients previously believed to have idiopathic HP have positive perinuclear ANCA (p-ANCA). This has been proposed as a separate disease entity. Co-occurrence of IgG4-RD and ANCA seropositivity has been reported in 4 cases in the literature to date, and this case serves to expand our current understanding of what likely represents a subpopulation of immune-mediated HP.