Hypertrophic Pachymeningitis as a Delayed Complication of Granulomatosis with Polyangiitis

A 69-year-old man presented with upper airway symptoms, multiple lung nodules and masses, proteinuria and hematuria, and an increased level of proteinase 3 anti-neutrophil cytoplasmic antibody (PR3-ANCA). Granulomatosis with polyangiitis (GPA) was diagnosed by a transbronchial lung biopsy. All of these symptoms were ameliorated and the level of PR3-ANCA declined following treatment with prednisolone and cyclophosphamide. The patient developed a headache 16 months after the onset of symptoms, and contrast-enhanced magnetic resonance imaging showed the thickening of the dura mater, which suggested that hypertrophic pachymeningitis (HP) had developed as a complication of GPA. HP can be a unique complication of GPA at recurrence, and can occur without the relapse of other lesions or an increase in PR3-ANCA level.