Idiopathic polymyositis
Synonym(s): Cervical ventroflexion, myopathy, stiff gait
Introduction
- Cause: suspected immune-mediated.
- Signs: weakness, reluctance to jump, stiff-stilted gait, muscle atrophy.
- Diagnosis: elevated CK, muscle biopsy, ruling-out infectious causes.
- Treatment: immune-suppressive therapy with prednisolone.
- Prognosis: fair although relapses may occur.
Presenting signs
- Weakness.
- Tendency to sit or lie down after walking short distances.
- Cervical ventro-flexion.
- Lameness.
- Reluctance to jump.
- Stiff-stilted gait.
- Muscle atrophy.
Acute presentation
- Sudden onset of weakness with ventro-flexion of the neck.
Geographic incidence
- None noted.
Age predisposition
- Mostly adult.
Breed/Species predisposition
- None.
Cost considerations
- Initial moderate cost outlay in accurate diagnosis of disease due to necessity for:
- Anesthesia.
- Electromyography.
- Serum titers for infectious diseases.
- Muscle biopsy.
- Long-term cost considerations include:
- Potential for life-long immunosuppressive therapy.
- Repeat muscle biopsies for treatment assessment if there is a relapse.
Special risks
- The diagnosis of the disease requires a work up necessitating anesthesia. No direct risk of anesthetizing a patient with polymyositis, but effect on strength of intercostal muscles and larynx, should be considered. Also, may be heightened risk of regurgitation Regurgitation when under anesthesia due to effect of disease on esophagus, not always clinically evident.
- Bone marrow suppression may result from use of more cytotoxic immunosuppressive medications, ie azathioprine Azathioprine.
Pathogenesis
Etiology
- Cause unknown, although responsiveness of disease to immunosuppressive therapy suggests immune-mediated pathogenesis.
- Can be paraneoplastic syndrome secondary to tumor such as thymoma Thymoma.
Predisposing factors
General
- None identified.
Pathophysiology
- Polymyositis suspected to be autoimmune in origin.
- Rarely can be secondary to thymoma.
Timecourse
- Timecourse of disease extremely variable depending on predominant clinical signs.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Ginman A A, Kline K L, Shelton G D (2009) Severe polymyositis and neuritis in a cat. J Am Vet Med Assoc 235 (2), 172-175 PubMed.
- Sura R, Hinckley L S, Risatti G R et al (2008) Fatal necrotising fasciitis and myositis in a cat associated with Streptococcus canis. Vet Rec 162 (14), 450-453 PubMed.
- Dickinson P J, LeCouteur R A (2004) Feline neuromuscular disorders. Vet Clin North Am Small Anim Pract 34 (6), 1307-1359 PubMed.
- Podell M (2002) Inflammatory myopathies. Vet Clin North Am: Sm Anim Pract 32 (1), 147-167 PubMed.