Idiopathic Orbital Inflammatory Pseudotumor With Bone Erosion

Purpose/Background:To report a rare patient with idiopathic orbital inflammatory pseudotumor showing obvious bone erosion of the orbital wall.Methods:Clinical features and imaging findings, orbital surgery, and histopathological examination are presented.Results:A 56-year-old Chinese man showed a gradually growing unilateral proptosis of the left eye for 6 months. Visual acuity, intraocular pressure, anterior segment, and fundi were normal in both eyes. Proptosis was 17mm in the right eye and 23mm in the left. No palpable mass was present on the left orbital rim. Ocular motility showed a moderate limitation of left adduction. Computed tomography scan revealed multifocal smoothly outlined homogeneous soft tissue masses measuring from 10x6 to 30x10mm with obvious bone destruction in the lateral and inferior walls of the left orbit. An anterior orbitotomy by an inferio-temporal skin incision was used to partially remove the mass. Histopathological evaluation confirmed the diagnosis of an idiopathic inflammatory pseudotumor. After surgery, administration of systemic corticosteroids was initiated, which resulted in a dramatic improvement in the proptosis and ocular movements. There was no recurrence as determined at 6 years postsurgery and visual acuity was 25/20 in both eyes.Conclusions:Idiopathic orbital inflammatory pseudotumor may show an orbital bone erosion, similar to that of soft-tissue malignancy or orbital metastasis.