Extraocular muscle myositis and restrictive strabismus in 10 dogs.

Ten cases of uni- or bilateral restrictive ventromedial strabismus in young dogs of different breeds are reported. Clinically, abnormalities were restricted to the extraocular muscles with sparing of the masticatory muscles and limb muscles. This was supported in some cases by imaging studies, electrophysiology, and immunocytochemical assay for antibodies against type 2M fibers. Histologically, there was variable lymphocytic plasmacytic mononuclear cell infiltration and fibrosis. This disorder is similar in many aspects to chronic masticatory myositis with focal myositis and subsequent fibrosis. Surgical correction may restore eye position and vision.