Journal of Veterinary Clinics (한국임상수의학회지)

The Korean Society of Veterinary Clinics (한국임상수의학회)
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Idiopathic Polymyositis Showing Nonspecific Clinical Signs that Mimicked Masticatory Myositis in a Dog

  • Soyoung Jung (Department of Veterinary Internal Medicine, College of Veterinary Medicine, Konkuk University) ;
  • Junghoon Park (Department of Veterinary Internal Medicine, Western Animal Medical Center) ;
  • Yeon-Jung Hong (Department of Veterinary Surgery, Western Animal Medical Center) ;
  • Aryung Nam (Department of Veterinary Internal Medicine, College of Veterinary Medicine, Konkuk University)
  • Received : 2024.09.09
  • Accepted : 2024.10.18
  • Published : 2024.10.31
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Abstract

Idiopathic polymyositis and masticatory myositis are autoimmune inflammatory myopathies seen in dogs. Here we report a case involving an 11-year-old spayed female mixed-breed dog with suspected masticatory myositis that was later confirmed to be idiopathic polymyositis. The dog presented with lethargy and reluctance to walk. Blood examination indicated markedly elevated creatine kinase and C-reactive protein levels. The owners were reluctant to proceed with advanced tests; however, the dog developed new clinical signs, including trismus. T2-weighted magnetic resonance imaging revealed hyperintensities in multiple muscle groups, with the most pronounced changes occurring in the masticatory muscles. During the waiting period for the results of serology for circulating autoantibodies against type 2M myofibers, oclacitinib was administered and slightly restored vitality and appetite. The antibody test result was negative, and histopathological examination of the temporalis muscle revealed severe inflammatory myopathy with fibroplasia. Although masticatory myositis was initially suspected on the basis of the MRI findings and the presence of trismus, the final diagnosis based on the overall clinical course and diagnostic test results was idiopathic polymyositis. Immunosuppressive treatment with prednisolone and mycophenolate mofetil substantially improved the clinical condition. The findings from this case suggest that, even in cases of idiopathic polymyositis exhibiting only nonspecific clinical signs, accurate diagnosis and timely treatment are essential to achieve satisfactory clinical outcomes.

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References

  1. Anderson JG, Harvey CE. Masticatory muscle myositis. J Vet Dent 1993; 10: 6-8.
  2. Averill DR Jr. Diseases of the muscle. Vet Clin North Am Small Anim Pract 1980; 10: 223-234.
  3. Banovic F, Tarigo J, Gordon H, Barber JP, Gogal RM Jr. Immunomodulatory in vitro effects of oclacitinib on canine T-cell proliferation and cytokine production. Vet Dermatol 2019; 30: 17-e6.
  4. Congiusta MC, Snyder C, Soukup JW, Apostolopoulos N. Novel management of masticatory myositis in three dogs with a selective Janus kinase (JAK-1) inhibitor. J Vet Dent 2024. doi: 10.1177/08987564231219925.
  5. Evans J, Levesque D, Shelton GD. Canine inflammatory myopathies: a clinicopathologic review of 200 cases. J Vet Intern Med 2004; 18: 679-691.
  6. Gonzales AJ, Bowman JW, Fici GJ, Zhang M, Mann DW, Mitton-Fry M. Oclacitinib (APOQUEL(®)) is a novel Janus kinase inhibitor with activity against cytokines involved in allergy. J Vet Pharmacol Ther 2014; 37: 317-324.
  7. Jeffery ND, Levine JM, Olby NJ, Stein VM. Intervertebral disk degeneration in dogs: consequences, diagnosis, treatment, and future directions. J Vet Intern Med 2013; 27: 1318-1333.
  8. Kornegay JN, Gorgacz EJ, Dawe DL, Bowen JM, White NA, DeBuysscher EV. Polymyositis in dogs. J Am Vet Med Assoc 1980; 176: 431-438.
  9. Melmed C, Shelton GD, Bergman R, Barton C. Masticatory muscle myositis: pathogenesis,diagnosis,and treatment. Compend Contin Educ Pract Vet 2004; 26: 590-605.
  10. Morozumi M, Oyama Y, Kurosu Y, Nakayama H, Goto N, Yasuda K, et al. Immune-mediated polymyositis in a dog. J Vet Med Sci 1991; 53: 511-512.
  11. Nelson RW, Couto CG. Small animal internal medicine. 6th ed. St. Louis: Elsevier. 2019: 1174-1176.
  12. Neumann J, Bilzer T. Evidence for MHC I-restricted CD8+ T-cell-mediated immunopathology in canine masticatory muscle myositis and polymyositis. Muscle Nerve 2006; 33: 215-224.
  13. Podell M. Inflammatory myopathies. Vet Clin North Am Small Anim Pract 2002; 32: 147-167.
  14. Pumarola M, Moore PF, Shelton GD. Canine inflammatory myopathy: analysis of cellular infiltrates. Muscle Nerve 2004; 29: 782-789.
  15. Shelton GD, Cardinet GH 3rd, Bandman E. Canine masticatory muscle disorders: a study of 29 cases. Muscle Nerve 1987; 10: 753-766.
  16. Troupel T, Van Caenegem N, Drougard C, Blanchard-Gutton N, Blot S. Generalised idiopathic polymyositis mimicking masticatory myositis in a dog. Vet Rec Case Rep 2022; 10: e452.
  17. Wohlsein JC, Tipold A. Steroid-responsive meningitis-arteritis: what have we learned since 2010? A narrative review. Vet J 2023; 300-302: 106030.
  18. Wu X, Li ZF, Brooks R, Komives EA, Torpey JW, Engvall E, et al. Autoantibodies in canine masticatory muscle myositis recognize a novel myosin binding protein-C family member. J Immunol 2007; 179: 4939-4944.