A case of MPO- and PR3-ANCA-positive hypertrophic cranial pachymeningitis with elevated serum IgG4.

We report a case of orbital tumor and hypertrophic cranial pachymeningitis in a 64-year-old woman, who was initially suspected to have IgG4-related disease because of an elevated level of serum IgG4 at onset. However, her condition was resistant to glucocorticoid therapy, and additional cyclophosphamide was necessary to control the disease activity. Additional features included elevated levels of serum myeloperoxidase (MPO) and proteinase-3-anti-neutrophil cytoplasmic antibody (PR3-ANCA), and biopsy specimens from the orbital mass revealed very few infiltrating IgG4-positive cells. Instead, rupture of the elastic layer of the arterial walls with neovascularization and a small number of giant cells were observed. Considering these findings and the clinical course, the disease was considered more likely to be ANCA-associated pachymeningitis with elevation of the serum IgG4 level.