We report the first documented case of IgG4-related inflammatory pseudotumours (IPTs) along the bilateral oculomotor nerves. A man in his 60s complained of decreased vision. He exhibited bilateral optic nerve atrophy without any extraocular movement deficits. MRI revealed enhanced masses that reached from the bilateral cavernous sinus to within the bilateral orbits. The tumours extended along the lines of the bilateral oculomotor nerves. The patient's serum level of IgG4 was high, 147 mg/dl. A biopsy specimen showed inflammatory cell-rich lesions against a collagenous stroma. Immunostaining revealed infiltration of CD138-positive plasma cells, which were mainly IgG and IgG4 positive. The IgG4/IgG ratio was greater than 0.4. These factors led us to a diagnosis of IgG4-related IPTs. Oral administration of prednisolone (30 mg/day) was started 3 months after the operation and continued for 6 months with gradual tapering. The tumour was significantly reduced by prednisolone.
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