Dynamic exophthalmos and lateral strabismus in a dog caused by masticatory muscle myositis

作者：Czerwinski Sarah L; Plummer Caryn E^*; Greenberg Shari M; Craft William F; Conway Julia A; Perez Mayrim L; Cooke Kirsten L; Winter Matthew D

来源：Veterinary Ophthalmology, 2015, 18(6): 515-520.

DOI：10.1111/vop.12260

• dog
• exophthalmos
• masticatory
• muscle
• myositis
• strabismus

Case descriptionA 5.5-year-old neutered male mixed-breed dog was presented for evaluation of a 5-month history of deviation of the right globe upon opening the mouth and a 1-month history of conjunctivitis in the same eye. Clinical findings, diagnostic imaging results, treatment and follow-up are described.
Clinical findingsWhen the mouth was opened, the right globe deviated rostrally and laterally. There was no pain or resistance to opening the mouth, or resistance to retropulsion of the globe. No other abnormalities were observed. Computed tomography was performed, revealing a contrast-enhancing region associated with the right masseter muscle impinging into the right orbit; this was more pronounced with the mouth open. Cytology revealed a small number of mildly to moderately atypical mesenchymal cells. Histopathology was consistent with polyphasic myositis, with a predominance of lymphocytes and plasma cells. No infectious agents were identified. Serum antibody titers for Toxoplasma gondii and Neospora caninum were negative. Serum titers for 2M antibody were positive at 1:500, consistent with a diagnosis of masticatory muscle myositis.
Treatment and outcomeTherapy with prednisone was initiated. During a follow-up period of 5months, there was no recurrence of clinical signs, and the dose of prednisone was reduced by 25%.
Clinical significanceTo the authors' knowledge, this is the first reported case of masticatory muscle myositis causing dynamic exophthalmos and strabismus in a dog.

• 出版日期2015-11