Eosinophilic Myositis is a rare disorder of dogs causing immune-mediated inflammation of the muscles of mastication.
Signalment
The average age of affected dog is 3 years old. Seen most commonly in German Shepherds and Weimaraners, there is no recorded sex predilection.
Clinical Signs
Bilateral symmetrical swelling of masseter, pterygoid and temporal muscles
Exopthalmos
Chemosis/eyelid odema
Third eyelid protrusion
Pain on opening jaws fully
A key difference from other orbital disease is that the clincial signs are bilateral
Diagnosis
Muscle biopsy provides definite diagnosis
Treatment
Immunosuppressive doses of steroids, azathioprine if needed.
Recovered animals may have permanent difficulty opening their jaws due to muscle scarring.
References
Maggs, D et al (2007) Slatter's Fundamentals Of Veterinary Ophthalmology (Fourth Edition) Saunders
Riis, Ronald C (2002) Small Animal Ophthalmology Secrets Hanley and Belfus, Inc