Eosinophilic Myositis

Eosinophilic Myositis is a rare disorder of dogs causing immune-mediated inflammation of the muscles of mastication. The aetiology is unknown. 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