Managing masticatory muscle myositis — an immune-mediated jaw muscle disease causing severe pain and dysfunction.
Masticatory muscle myositis causes significant welfare impairment through jaw pain, inability to open the mouth, and difficulty eating. In the acute phase, jaw muscles are severely swollen, painful, and warm — dogs cry when eating, refuse hard food, and resist mouth examination. The acute pain is intense and clearly debilitating.
The chronic welfare concern is fibrosis. If the acute phase is not treated promptly with adequate immunosuppression, inflammatory damage leads to fibrotic replacement of jaw muscle. Fibrotic muscles cannot be stretched — the result is permanent jaw restriction (trismus) that makes eating difficult or impossible without intervention. Jaw stretching under anaesthesia can partially restore opening in early fibrosis, but established contracture is difficult to reverse.
Early, aggressive immunosuppressive treatment with prednisolone achieves excellent welfare outcomes. Most dogs treated promptly in the acute phase recover full jaw function without fibrosis. Treatment must be maintained long-term with gradual dose reduction to prevent relapse. 2M antibody testing confirms the diagnosis and can guide treatment decisions.