[Orbital apex syndrome due to relapse during steroid tapering in a patient with MPO-ANCA-positive IgG4-related hypertrophic pachymeningitis].

A 75-year-old man developed hearing loss and hoarseness; 5 months later, he suffered from headache and loss of appetite. A blood test showed an inflammatory reaction, a high level of serum IgG4 (254.0 mg/dl), and positive reaction for MPO-ANCA. Gadolinium enhanced T1 weighted head magnetic resonance imaging (MRI) revealed dural thickening with marked enhancement. Infiltration of lymphocytes and anti-IgG4-positive plasma cells were detected in the dura mater by meningeal biopsy; thus, he was diagnosed with MPO-ANCA-positive IgG4-related hypertrophic pachymeningitis. His clinical manifestations, and serologic and MRI findings improved with steroid treatment; however, they recurred during steroid tapering and he presented with right orbital apex syndrome. We then added an immunosuppressive drug to his regimen. It was difficult to reduce the symptoms of this case, with oral steroid monotherapy, and its combination with an immunosuppressive drug was necessary.