[Extraocular myositis and comparative pathology: two case reports in the dog]

Two cases of extraocular myositis in dogs are reported in a golden retriever and an Australian shepherd. This condition is characterized by sudden bilateral exophthalmos, the absence of pain and third eyelid protrusion, orbital sonography showing the enlargement of extraocular muscles, and a quick response to systemic steroids at an anti-inflammatory dose. The literature review reports a breed predisposition in the golden retriever, mainly in females. Histopathologic evaluations confirm the inflammation of one or several extraocular muscles. Chronic disease was also described. Canine extraocular myositis shows some resemblance to Graves ophthalmopathy but can better be compared to idiopathic orbital myositis. Both disorders are probably the consequence of an immune dysfunction that still has to be discovered.