Features of ophthalmic, magnetic resonance imaging, and histopathology of a feline case of idiopathic sclerosing orbital pseudotumor

In the present report, we describe a case of sclerosing orbital pseudotumor in an 11‐year‐old castrated male American Shorthair cat. Ophthalmic exam showed lagophthalmos, retracted right upper eyelid, and resistant to retropulsion in his right eye. Under magnetic resonance imaging (MRI) scans, increased volume of the extraocular muscles (EOMs) of the right eye was prominent. Immunosuppressive dosage of prednisolone partially ameliorated the clinical signs, but some clinical signs were still gradually progressive or persistent. In the second MRI scan, decreased diameter of the thickened right extraocular muscles was found. After the third MRI scan, enucleation of the right eye was performed due to substantial adverse effects of systemic steroid therapy. Histopathological examination revealed no evidence of neoplastic transformation nor infection. Feline restrictive orbital myofibroblastic sarcoma (FROMS) was therefore excluded, suggesting unknown causes of extensive fibrotic changes in the right orbit of the affected cat.