A Case of Canine Immune-Mediated Polymyositis: Update of the diagnosis and clinical evaluation

A Case of Canine Immune-Mediated Polymyositis: Update of the diagnosis and clinical evaluation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Case Report A Case of Canine Immune-Mediated Polymyositis: Update of the diagnosis and clinical evaluation Jungwoo Han, KeunHwan Jang, Seung-Bum Cho, SuYeon Kim, Songju Oh, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4785771/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 10 Dec, 2024 Read the published version in BMC Veterinary Research → Version 1 posted 10 You are reading this latest preprint version Abstract 1. Background Inflammatory myopathy is generally categorized into generalized inflammatory myopathies (gIM), which affect muscles throughout the body, and focal inflammatory myopathies (fIM), which are localized to specific muscles or muscle groups. This report details a case of immune-mediated polymyositis in a dog, successfully diagnosed using MRI and IHC and managed with immunosuppressive therapy. 2. Case presentation A 5-year-old castrated male Poodle was admitted to a hospital presenting with lethargy and exercise intolerance. Biochemical analysis revealed significantly elevated serum levels of aspartate aminotransferase (AST) and creatine kinase (CK). Physical examination showed muscle atrophy in the hind legs, but further orthopedic and neurological examinations identified no additional abnormalities. MRI demonstrated hyperintense and heterogeneous signal changes across the muscles, including contrast enhancement, suggesting polymyositis. This diagnosis was confirmed through histopathological examination, which revealed inflammatory lesions with fibrous tissue proliferation within the muscle tissue. 3. Conclusions The dog was diagnosed with immune-mediated polymyositis and treatment was initiated with prednisolone (Solondo ® , Yuhan Pharmaceuticals) at 1 mg/kg twice daily and azathioprine (Immuthera ® , Celltrion Pharmaceuticals) at 2 mg/kg once daily. Following the administration of these immunosuppressive agents, CK levels returned to normal, and the dog’s exercise intolerance and lethargy resolved. The thickness of the hind legs also increased progressively. The dog has maintained an improved condition under continued immunosuppressive therapy for four months. This case highlights the critical role of MRI and immunohistochemistry in diagnosing immune-mediated polymyositis, demonstrating their superiority over conventional electromyography (EMG) in this context. Dog Polymyositis Immune-mediated MRI Figures Figure 1 Figure 2 Figure 3 Figure 4 Background Inflammatory myopathy is a disease characterized by non-purulent cellular infiltration of skeletal muscle. Similar to humans, myositis in veterinary medicine is classified based on its distribution. It is generally categorized into generalized inflammatory myopathies (gIM), which affect muscles throughout the body, and focal inflammatory myopathies (fIM), which are localized to specific muscles or muscle groups ( 1 ). Conditions such as extraocular myositis (EOM), masticatory myositis (MMM), and dermatomyositis (DM) represent focal inflammatory myopathies in dogs. Generalized inflammatory myopathies, including polymyositis—a type of generalized myositis—are typically immune-mediated ( 2 ). Other potential causes include bacterial agents, parasites such as protozoa, rickettsia, spirochetes, and paraneoplastic syndromes ( 1 ). Although specific data on the prevalence of polymyositis in dogs is lacking, it is estimated to affect about 0.01% of the human population, indicating its rarity in both species ( 3 ). To diagnose polymyositis in human medicine, several criteria must be met: 1) clinical signs such as muscle pain or weakness, 2) elevated serum muscle enzymes, including creatine kinase (CK) and aspartate aminotransferase (AST), 3) electromyographic (EMG) abnormalities, and 4) histopathological evidence of muscle necrosis and inflammation ( 4 , 5 ). Additionally, magnetic resonance imaging (MRI) and immunohistochemistry (IHC) are valuable diagnostic tools for polymyositis ( 6 – 9 ). This report details a case of immune-mediated polymyositis in a dog, successfully diagnosed using MRI and IHC and managed with immunosuppressive therapy. Case presentation A 5-year-old castrated male Poodle presented at the veterinary hospital exhibiting lethargy and exercise intolerance. The physical examination revealed muscle atrophy in the hind legs and enlargement of the left popliteal lymph node, measuring approximately 10.6 x 5.2 mm. Biochemical analysis showed elevated serum levels of aspartate aminotransferase (AST) at 509 U/L (reference range 0–50 U/L) and CK levels that exceeded the measurable limit (reference range 10–200 U/L). Neurological assessment elicited a pain response at the spinal T12-L1 level, and spinal radiographs indicated slight narrowing of this area. Further orthopedic and neurological evaluations did not reveal any specific abnormalities. Given these findings, intervertebral disc disease (IVDD) was initially suspected. MRI was performed to confirm this diagnosis. However, MRI did not support IVDD but instead showed distinct hyperintensity on T2-weighted and T2-STIR images, and iso-to-hyperintensity on T1-weighted images across general muscle areas. There were signal changes throughout the skeletal muscles, including the bilateral masticatory, paravertebral, gluteal, and proximal tibial muscles. Post-contrast imaging revealed uneven but distinct enhancement following contrast administration (Fig. 1 A, 1 B), suggesting widespread muscle inflammation, potentially indicative of polymyositis. To verify this diagnosis, a muscle biopsy was taken from the most visibly affected areas, the bilateral biceps femoris muscles. Histopathological analysis of these sites showed infiltration by mononuclear cells such as lymphocytes, plasma cells, and macrophages, alongside partial degeneration of the muscle tissue (Fig. 2 A). No neoplastic changes or pathogens were detected on hematoxylin and eosin (H&E) staining. Immunohistochemistry was conducted using anti-CD8 antibody (ab17147, Abcam, Cambridge, UK), anti-CD4 antibody (10B5, Genetex, CA, USA), and anti-Vascular Endothelial Growth Factor antibody (M7273, Dako, Glostrup, Denmark) to further explore the nature of the inflammatory infiltrate. The immunohistochemistry results for CD4, CD8, and VEGF were positive, indicating a T cell-mediated immune response and angiogenesis in the inflamed lesions (Fig. 3 A, 3 B, 3 C). Based on the clinical presentation and diagnostic findings, the dog was diagnosed with immune-mediated polymyositis. For the management of the condition, immunosuppressants were administered, including prednisolone (1 mg/kg PO bid; Solondo® tablet, Yuhan, Seoul, Korea) and azathioprine (2 mg/kg PO sid; Immuthera® tablet, Celltrion Pharmaceuticals, Incheon, Korea). One week following the administration of these agents, a significant reduction in serum CK levels was observed, decreasing from 2,815 to 108 (reference range: 10–200). Concurrently, the patient’s tolerance for walking during strolls extended from approximately 5 minutes to 20 minutes. Additionally, the circumference of the previously atrophied hind leg muscles increased from 11.7 cm to 17.1 cm on the left hind leg and from 12.1 cm to 19.2 cm on the right hind leg. Azathioprine-induced myelosuppression led to a decrease in platelet count from 358K/µL to 168K/µL (reference range: 148K/µL–484K/µL), which lies at the lower limit of the normal range. Consequently, azathioprine was replaced with cyclosporine (5 mg/kg PO, BID; Cipol-N, Chong Kun Dang Pharm, Cheonan, Chungnam, Korea), resulting in a normalization of the platelet count to 454K/µL. After six months of management, there was a notable alleviation in exercise intolerance, and serum CK levels have stabilized within the normal range. The circumference of the bilateral hind legs has continued to increase consistently, remaining within normal limits with no abnormalities observed in gait (Fig. 4 A, 4 B, 4 C). Discussion and conclusions This case report describes the successful diagnosis and clinical management of immune-mediated polymyositis in a Poodle. MRI played a crucial role in identifying muscle inflammation. While electromyography (EMG) is generally more practical, MRI is recommended for confirming suspected cases of myositis ( 9 ). Immunohistochemical evaluation was instrumental in diagnosing this case. It is essential to recognize the significance of immune cell infiltration in immune-mediated polymyositis ( 7 ). The goal of this evaluation is to detect the expression of major histocompatibility complex class I (MHC-1) and the presence of T cells and macrophages in canine polymyositis ( 1 , 7 ). Previous research has shown that inflammatory cells infiltrating the muscles in cases of immune-mediated polymyositis are predominantly T lymphocytes, mainly CD8 + and to a lesser extent CD4 + ( 1 , 10 – 11 ). Immunohistochemistry (IHC) involved the use of CD4 to identify helper T cells, CD8 for cytotoxic T cells, and vascular endothelial growth factor (VEGF) as a marker for potent endothelial angiogenic growth factors ( 1 , 10 , 12 ). The IHC results indicated that CD8 + T cells did not exhibit a significantly larger proportion of positive reactions compared to CD4 + T cells. In polymyositis, there is evidence that CD8 + T cells with cytotoxic properties target and attack muscle fibers expressing MHC-1 antigens ( 13 ). Following activation, auto-aggressive CD8 + T cells release perforin granules, which cause muscle fiber necrosis ( 14 ). CD4 + T cells are also implicated in autoimmune reactions, differentiating into cells capable of cytotoxic effects through the expression of perforin and granzymes ( 11 ). VEGF is critical in angiogenesis, with particular importance in wound healing and tissue regeneration ( 15 ). To date, VEGF has not been utilized for diagnosing polymyositis in dogs. In humans, however, research indicates that VEGF expression can differentiate between the acute and chronic stages of the disease ( 12 , 16 ). Drawing on these findings, and given the pathological similarities between canine and human polymyositis, this case can be classified as acute immune-mediated polymyositis. In human polymyositis, analysis of myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) plays a significant role in diagnosis ( 11 ). However, studies on MSA and MAA in dogs are currently insufficient, necessitating further research ( 10 ). Previous reports suggest that a regimen combining immunosuppressive agents is preferable to minimize long-term side effects associated with corticosteroids ( 17 ). Prednisolone and azathioprine are the most commonly used combination, constituting 86% of cases ( 17 ). In human medicine, azathioprine is often the first choice as a steroid-sparing immunosuppressive agent ( 18 , 19 ). Similarly, the efficacy of cyclosporine in treating polymyositis has been well-documented in human medicine, with veterinary reports also confirming its effectiveness in canine polymyositis ( 10 , 18 , 20 – 22 ). Clinical improvement was noted after the administration of cyclosporine and steroids, with no specific side effects reported. Abbreviations gIM generalized inflammatory myopathies fIM focal inflammatory myopathies EOM Extraocular myositis MMM Masticatory myositis DM dermatomyositis CK Creatine kinase AST Aspartate aminotransferase EMG Electromyographic MRI Magnetic resonance imaging IHC Immunohistochemistry Declarations Ethics approval and consent to participate Not applicable Consent for publication Written informed consent was obtained from the dog’s owner. Availability of data and materials All Data supporting our findings are included in this study. Competing interests The authors declare that they have no competing interests Funding This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2023R1A2C1005348). Authors' contributions JW. H was the main contributor to the writing of the manuscript. KH. J, SB. C, SY. K, SJ. O and HJ. K performed the study. JW. H, SJ. O, and HJ. K analyzed the data and conducted clinical management of the case. HJ-K supervised the case management, edited the manuscript. All the authors have read and approved the final version of the manuscript. Acknowledgement The authors are grateful to the dog and the dog owner for participating in our report. Also, the authors would like to express their appreciation to the reviewers and editors for their insightful feedback. References Evans J, Levesque D, Shelton GD. Canine inflammatory myopathies: a clinicopathologic review of 200 cases. J Vet Intern Med. 2004;18(5):679-691. Dalakas MC, Hohlfeld R. Polymyositis and dermatomyositis. Lancet. 2003;362(9388):971-982. Shelton GD. From dog to man: the broad spectrum of inflammatory myopathies. Neuromuscul Disord. 2007;17(9-10):663-670. Kornegay JN, Gorgacz EJ, Dawe DL, Bowen JM, White NA, et al. Polymyositis in dogs. Kidney. 1980;90:602. MOROZUMI M, OYAMA Y, KUROSU Y, NAKAYAMA H, GOTO N, et al. Immune-mediated polymyositis in a dog. J Vet Med Sci. 1991;53(3):511-512. Pumarola M, Moore PF, Shelton GD. Canine inflammatory myopathy: analysis of cellular infiltrates. Muscle Nerve. 2004;29(6):782-789. Verma R, Paliwal VK. Idiopathic inflammatory myopathy: From muscle biopsy to serology. Indian J Rheumatol. 2020;15(Suppl 2) Lampa J, Nennesmo I, Einarsdottir H, Lundberg I. MRI guided muscle biopsy confirmed polymyositis diagnosis in a patient with interstitial lung disease. Ann Rheum Dis. 2001;60(4):423-426. Platt SR, McConnell JF, Garosi LS, Ladlow J, De Stefani A, et al. Magnetic resonance imaging in the diagnosis of canine inflammatory myopathies in three dogs. Vet Radiol Ultrasound. 2006;47(6):532-537. 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(4) Malmström V, Venalis P, Albrecht I. T cells in myositis. Arthritis Res Ther. 2012;14:1-6. Grundtman C, Tham E, Ulfgren AK, Lundberg IE. Vascular endothelial growth factor is highly expressed in muscle tissue of patients with polymyositis and patients with dermatomyositis. Arthritis Rheum. 2008;58(10):3224-3238. 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(2):215-224. Yang SH, Chang C, Lian ZX. Polymyositis and dermatomyositis - challenges in diagnosis and management. J Transl Autoimmun. 2019;2:100018. Ferrara N. Vascular endothelial growth factor: basic science and clinical progress. Endocr Rev. 2004;25(4):581-611. Lundberg IE. Vascular endothelial growth factor (VEGF) expression in muscle tissue and the effect of corticosteroid therapy in patients with poly- and dermatomyositis. Arthritis Res Ther. 2002;4(Suppl 1):12. Tauro A, Addicott D, Foale RD, Bowman C, Hahn C, et al. Clinical features of idiopathic inflammatory polymyopathy in the Hungarian Vizsla. BMC Vet Res. 2015;11(1):1-13. Foreman M, Cherubini GB. Dexamethasone can be safely and effectively used for treatment of masticatory muscle myositis in dogs. Top Companion Anim Med. 2021;44:100538. Oddis CV. Update on the pharmacological treatment of adult myositis. J Intern Med. 2016;280(1):63-74. Alijotas J, Barquinero J, Ordi J, Vilardell M. Polymyositis and cyclosporin A. Ann Rheum Dis. 1990;49(1):66. Van der Meer S, Imhof JW, Borleffs JC. Cyclosporin for polymyositis. Ann Rheum Dis. 1986;45(7):612. Chandra BS, Prabavathy AA, Vijayalakshmi P, Selvi D, Rajkumar K, et al. Polymyositis in a Doberman bitch. Indian J Anim Hlth. 2017;56(2):279-282. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 10 Dec, 2024 Read the published version in BMC Veterinary Research → Version 1 posted Editorial decision: Revision requested 07 Aug, 2024 Reviews received at journal 03 Aug, 2024 Reviews received at journal 02 Aug, 2024 Reviewers agreed at journal 31 Jul, 2024 Reviewers agreed at journal 30 Jul, 2024 Reviewers invited by journal 30 Jul, 2024 Editor invited by journal 29 Jul, 2024 Editor assigned by journal 29 Jul, 2024 Submission checks completed at journal 23 Jul, 2024 First submitted to journal 23 Jul, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4785771","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":337134411,"identity":"411fa5be-7e98-471e-a296-aff6c150e71f","order_by":0,"name":"Jungwoo Han","email":"","orcid":"","institution":"Chonnam National University","correspondingAuthor":false,"prefix":"","firstName":"Jungwoo","middleName":"","lastName":"Han","suffix":""},{"id":337134412,"identity":"77d8c95c-091a-4268-adf1-e2de204884c1","order_by":1,"name":"KeunHwan Jang","email":"","orcid":"","institution":"Chonnam National University","correspondingAuthor":false,"prefix":"","firstName":"KeunHwan","middleName":"","lastName":"Jang","suffix":""},{"id":337134413,"identity":"699ac932-8b61-42b6-a475-dec0271b2d4b","order_by":2,"name":"Seung-Bum Cho","email":"","orcid":"","institution":"Chonnam National University","correspondingAuthor":false,"prefix":"","firstName":"Seung-Bum","middleName":"","lastName":"Cho","suffix":""},{"id":337134414,"identity":"6bb5393d-ec82-4812-bb64-545f18fa019d","order_by":3,"name":"SuYeon Kim","email":"","orcid":"","institution":"Chonnam National University","correspondingAuthor":false,"prefix":"","firstName":"SuYeon","middleName":"","lastName":"Kim","suffix":""},{"id":337134415,"identity":"614452ea-7e26-479e-9b11-7c882a4e527d","order_by":4,"name":"Songju Oh","email":"","orcid":"","institution":"Chonnam National University","correspondingAuthor":false,"prefix":"","firstName":"Songju","middleName":"","lastName":"Oh","suffix":""},{"id":337134416,"identity":"8ab27f9f-ba2c-46a5-9e68-02bc31bc2af0","order_by":5,"name":"Ha-Jung Kim","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4ElEQVRIie3RvWoCQRSG4W8Z0MKfbb9hYK9hw8KijddiWPAatpC4ENFGrAUvQ1DLk8ZqNG3KXIJVypBdFdLtbBnIvMUUh/PAgQF8vj8YFVpgThVCHpNmxA7aumhMUJJgnoex/E7q08vO5HNY0CRv5xMxHUFvpZ4Y1TvE+sgklcuEOGUw/XE9iVRvT22ZpWJToiWIuo7D7mTB2a6oyHcDYh5ExShJsBAYF9GvJaGlothk8LzOunrlIHw/7w3zFxVu7NPH9WsU0TpIlbp9BQUYA66z7gXX6g2LRss+n8/3D/sBe3k3NCIM6fYAAAAASUVORK5CYII=","orcid":"","institution":"Chonnam National University","correspondingAuthor":true,"prefix":"","firstName":"Ha-Jung","middleName":"","lastName":"Kim","suffix":""}],"badges":[],"createdAt":"2024-07-23 05:24:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4785771/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4785771/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12917-024-04356-6","type":"published","date":"2024-12-10T15:57:34+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":63272768,"identity":"4872fc0f-f2ae-4e7e-97ee-f34f88a497bb","added_by":"auto","created_at":"2024-08-26 11:34:45","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":421946,"visible":true,"origin":"","legend":"\u003cp\u003ePhotographs of MRI showing distinct hyperintensity on T2-weighted images, indicating muscle inflammation (red arrows). Includes the bilateral masticatory muscles (A) and gluteal muscles (B).\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4785771/v1/73ecc1cd49ea0a95fe48879d.jpeg"},{"id":63272767,"identity":"f903c43b-6a6a-4d65-8199-f952d00dbac0","added_by":"auto","created_at":"2024-08-26 11:34:45","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":866105,"visible":true,"origin":"","legend":"\u003cp\u003eHistological analysis of the biceps femoris muscle using hematoxylin-eosin staining. At low magnification (×20), the muscle tissue exhibits partial degenerative changes and infiltration of inflammatory cells (A). At high magnification (×250), there is infiltration of mononuclear cells (black arrows), including lymphocytes, plasma cells, and macrophages within the lesion (B).\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4785771/v1/dee81b6bae745ee882edb953.jpeg"},{"id":63272766,"identity":"eccb699e-9a1b-4dea-b15c-589c65f289ea","added_by":"auto","created_at":"2024-08-26 11:34:44","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1271600,"visible":true,"origin":"","legend":"\u003cp\u003eImmunohistochemical analysis of the left biceps femoris muscle. CD8-positive staining indicates the presence of cytotoxic T cells (A), CD4-positive staining indicates helper T cells (B), and VEGF-positive staining suggests an angiogenic reaction (C).\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4785771/v1/41257fb028f8953774a37ddd.jpeg"},{"id":63272765,"identity":"827af1ca-06a8-491e-8710-8d02009cc46f","added_by":"auto","created_at":"2024-08-26 11:34:44","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":126610,"visible":true,"origin":"","legend":"\u003cp\u003eThe patient’s serum creatine kinase (CK) levels during the therapeutic monitoring period. After diagnosis of polymyositis, immunosuppressive drugs were administered (A). The patient’s bilateral hind limb circumference consistently increased during the therapeutic monitoring period (B).\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-4785771/v1/21905488b0542dcf474f419d.jpeg"},{"id":71552376,"identity":"d7e2ee0b-a676-40b3-a432-f16496ecdd6c","added_by":"auto","created_at":"2024-12-16 16:05:36","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2967764,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4785771/v1/e26683cf-e670-45d4-8b9d-49ed216060a9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"A Case of Canine Immune-Mediated Polymyositis: Update of the diagnosis and clinical evaluation","fulltext":[{"header":"Background","content":"\u003cp\u003eInflammatory myopathy is a disease characterized by non-purulent cellular infiltration of skeletal muscle. Similar to humans, myositis in veterinary medicine is classified based on its distribution. It is generally categorized into generalized inflammatory myopathies (gIM), which affect muscles throughout the body, and focal inflammatory myopathies (fIM), which are localized to specific muscles or muscle groups (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). Conditions such as extraocular myositis (EOM), masticatory myositis (MMM), and dermatomyositis (DM) represent focal inflammatory myopathies in dogs. Generalized inflammatory myopathies, including polymyositis\u0026mdash;a type of generalized myositis\u0026mdash;are typically immune-mediated (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Other potential causes include bacterial agents, parasites such as protozoa, rickettsia, spirochetes, and paraneoplastic syndromes (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). Although specific data on the prevalence of polymyositis in dogs is lacking, it is estimated to affect about 0.01% of the human population, indicating its rarity in both species (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo diagnose polymyositis in human medicine, several criteria must be met: 1) clinical signs such as muscle pain or weakness, 2) elevated serum muscle enzymes, including creatine kinase (CK) and aspartate aminotransferase (AST), 3) electromyographic (EMG) abnormalities, and 4) histopathological evidence of muscle necrosis and inflammation (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Additionally, magnetic resonance imaging (MRI) and immunohistochemistry (IHC) are valuable diagnostic tools for polymyositis (\u003cspan additionalcitationids=\"CR7 CR8\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis report details a case of immune-mediated polymyositis in a dog, successfully diagnosed using MRI and IHC and managed with immunosuppressive therapy.\u003c/p\u003e"},{"header":"Case presentation","content":"\u003cp\u003eA 5-year-old castrated male Poodle presented at the veterinary hospital exhibiting lethargy and exercise intolerance. The physical examination revealed muscle atrophy in the hind legs and enlargement of the left popliteal lymph node, measuring approximately 10.6 x 5.2 mm. Biochemical analysis showed elevated serum levels of aspartate aminotransferase (AST) at 509 U/L (reference range 0\u0026ndash;50 U/L) and CK levels that exceeded the measurable limit (reference range 10\u0026ndash;200 U/L). Neurological assessment elicited a pain response at the spinal T12-L1 level, and spinal radiographs indicated slight narrowing of this area. Further orthopedic and neurological evaluations did not reveal any specific abnormalities. Given these findings, intervertebral disc disease (IVDD) was initially suspected. MRI was performed to confirm this diagnosis. However, MRI did not support IVDD but instead showed distinct hyperintensity on T2-weighted and T2-STIR images, and iso-to-hyperintensity on T1-weighted images across general muscle areas. There were signal changes throughout the skeletal muscles, including the bilateral masticatory, paravertebral, gluteal, and proximal tibial muscles. Post-contrast imaging revealed uneven but distinct enhancement following contrast administration (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB), suggesting widespread muscle inflammation, potentially indicative of polymyositis. To verify this diagnosis, a muscle biopsy was taken from the most visibly affected areas, the bilateral biceps femoris muscles. Histopathological analysis of these sites showed infiltration by mononuclear cells such as lymphocytes, plasma cells, and macrophages, alongside partial degeneration of the muscle tissue (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). No neoplastic changes or pathogens were detected on hematoxylin and eosin (H\u0026amp;E) staining. Immunohistochemistry was conducted using anti-CD8 antibody (ab17147, Abcam, Cambridge, UK), anti-CD4 antibody (10B5, Genetex, CA, USA), and anti-Vascular Endothelial Growth Factor antibody (M7273, Dako, Glostrup, Denmark) to further explore the nature of the inflammatory infiltrate. The immunohistochemistry results for CD4, CD8, and VEGF were positive, indicating a T cell-mediated immune response and angiogenesis in the inflamed lesions (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC). Based on the clinical presentation and diagnostic findings, the dog was diagnosed with immune-mediated polymyositis.\u003c/p\u003e\u003cp\u003eFor the management of the condition, immunosuppressants were administered, including prednisolone (1 mg/kg PO bid; Solondo\u0026reg; tablet, Yuhan, Seoul, Korea) and azathioprine (2 mg/kg PO sid; Immuthera\u0026reg; tablet, Celltrion Pharmaceuticals, Incheon, Korea). One week following the administration of these agents, a significant reduction in serum CK levels was observed, decreasing from 2,815 to 108 (reference range: 10\u0026ndash;200). Concurrently, the patient\u0026rsquo;s tolerance for walking during strolls extended from approximately 5 minutes to 20 minutes. Additionally, the circumference of the previously atrophied hind leg muscles increased from 11.7 cm to 17.1 cm on the left hind leg and from 12.1 cm to 19.2 cm on the right hind leg.\u003c/p\u003e \u003cp\u003eAzathioprine-induced myelosuppression led to a decrease in platelet count from 358K/\u0026micro;L to 168K/\u0026micro;L (reference range: 148K/\u0026micro;L\u0026ndash;484K/\u0026micro;L), which lies at the lower limit of the normal range. Consequently, azathioprine was replaced with cyclosporine (5 mg/kg PO, BID; Cipol-N, Chong Kun Dang Pharm, Cheonan, Chungnam, Korea), resulting in a normalization of the platelet count to 454K/\u0026micro;L. After six months of management, there was a notable alleviation in exercise intolerance, and serum CK levels have stabilized within the normal range. The circumference of the bilateral hind legs has continued to increase consistently, remaining within normal limits with no abnormalities observed in gait (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion and conclusions","content":"\u003cp\u003eThis case report describes the successful diagnosis and clinical management of immune-mediated polymyositis in a Poodle. MRI played a crucial role in identifying muscle inflammation. While electromyography (EMG) is generally more practical, MRI is recommended for confirming suspected cases of myositis (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eImmunohistochemical evaluation was instrumental in diagnosing this case. It is essential to recognize the significance of immune cell infiltration in immune-mediated polymyositis (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). The goal of this evaluation is to detect the expression of major histocompatibility complex class I (MHC-1) and the presence of T cells and macrophages in canine polymyositis (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). Previous research has shown that inflammatory cells infiltrating the muscles in cases of immune-mediated polymyositis are predominantly T lymphocytes, mainly CD8\u003csup\u003e+\u003c/sup\u003e and to a lesser extent CD4\u003csup\u003e+\u003c/sup\u003e (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Immunohistochemistry (IHC) involved the use of CD4 to identify helper T cells, CD8 for cytotoxic T cells, and vascular endothelial growth factor (VEGF) as a marker for potent endothelial angiogenic growth factors (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe IHC results indicated that CD8\u003csup\u003e+\u003c/sup\u003e T cells did not exhibit a significantly larger proportion of positive reactions compared to CD4\u003csup\u003e+\u003c/sup\u003e T cells. In polymyositis, there is evidence that CD8\u003csup\u003e+\u003c/sup\u003e T cells with cytotoxic properties target and attack muscle fibers expressing MHC-1 antigens (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). Following activation, auto-aggressive CD8\u003csup\u003e+\u003c/sup\u003e T cells release perforin granules, which cause muscle fiber necrosis (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). CD4\u003csup\u003e+\u003c/sup\u003e T cells are also implicated in autoimmune reactions, differentiating into cells capable of cytotoxic effects through the expression of perforin and granzymes (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eVEGF is critical in angiogenesis, with particular importance in wound healing and tissue regeneration (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). To date, VEGF has not been utilized for diagnosing polymyositis in dogs. In humans, however, research indicates that VEGF expression can differentiate between the acute and chronic stages of the disease (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Drawing on these findings, and given the pathological similarities between canine and human polymyositis, this case can be classified as acute immune-mediated polymyositis.\u003c/p\u003e \u003cp\u003eIn human polymyositis, analysis of myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) plays a significant role in diagnosis (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). However, studies on MSA and MAA in dogs are currently insufficient, necessitating further research (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePrevious reports suggest that a regimen combining immunosuppressive agents is preferable to minimize long-term side effects associated with corticosteroids (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). Prednisolone and azathioprine are the most commonly used combination, constituting 86% of cases (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). In human medicine, azathioprine is often the first choice as a steroid-sparing immunosuppressive agent (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). Similarly, the efficacy of cyclosporine in treating polymyositis has been well-documented in human medicine, with veterinary reports also confirming its effectiveness in canine polymyositis (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). Clinical improvement was noted after the administration of cyclosporine and steroids, with no specific side effects reported.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003egIM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003egeneralized inflammatory myopathies\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003efIM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003efocal inflammatory myopathies\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eEOM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eExtraocular myositis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMMM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMasticatory myositis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eDM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003edermatomyositis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCK\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eCreatine kinase\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eAST\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eAspartate aminotransferase\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eEMG\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eElectromyographic\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMRI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMagnetic resonance imaging\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eIHC\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eImmunohistochemistry\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWritten informed consent was obtained from the dog\u0026rsquo;s owner.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll Data supporting our findings are included in this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2023R1A2C1005348).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJW. H was the main contributor to the writing of the manuscript. KH. J, SB. C, SY. K, SJ. O and HJ. K performed the study. JW. H, SJ. O, and HJ. K analyzed the data and conducted clinical management of the case. HJ-K supervised the case management, edited the manuscript. All the authors have read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors are grateful to the dog and the dog owner for participating in our report. Also, the authors would like to express their appreciation to the reviewers and editors for their insightful feedback.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eEvans J, Levesque D, Shelton GD. Canine inflammatory myopathies: a clinicopathologic review of 200 cases. J Vet Intern Med. 2004;18(5):679-691.\u003c/li\u003e\n\u003cli\u003eDalakas MC, Hohlfeld R. Polymyositis and dermatomyositis. Lancet. 2003;362(9388):971-982.\u003c/li\u003e\n\u003cli\u003eShelton GD. From dog to man: the broad spectrum of inflammatory myopathies. Neuromuscul Disord. 2007;17(9-10):663-670.\u003c/li\u003e\n\u003cli\u003eKornegay JN, Gorgacz EJ, Dawe DL, Bowen JM, White NA, et al. Polymyositis in dogs. Kidney. 1980;90:602.\u003c/li\u003e\n\u003cli\u003eMOROZUMI M, OYAMA Y, KUROSU Y, NAKAYAMA H, GOTO N, et al. Immune-mediated polymyositis in a dog. J Vet Med Sci. 1991;53(3):511-512.\u003c/li\u003e\n\u003cli\u003ePumarola M, Moore PF, Shelton GD. Canine inflammatory myopathy: analysis of cellular infiltrates. Muscle Nerve. 2004;29(6):782-789.\u003c/li\u003e\n\u003cli\u003eVerma R, Paliwal VK. Idiopathic inflammatory myopathy: From muscle biopsy to serology. Indian J Rheumatol. 2020;15(Suppl 2)\u003c/li\u003e\n\u003cli\u003eLampa J, Nennesmo I, Einarsdottir H, Lundberg I. MRI guided muscle biopsy confirmed polymyositis diagnosis in a patient with interstitial lung disease. Ann Rheum Dis. 2001;60(4):423-426.\u003c/li\u003e\n\u003cli\u003ePlatt SR, McConnell JF, Garosi LS, Ladlow J, De Stefani A, et al. Magnetic resonance imaging in the diagnosis of canine inflammatory myopathies in three dogs. Vet Radiol Ultrasound. 2006;47(6):532-537.\u003c/li\u003e\n\u003cli\u003eTroupel 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(4)\u003c/li\u003e\n\u003cli\u003eMalmstr\u0026ouml;m V, Venalis P, Albrecht I. T cells in myositis. Arthritis Res Ther. 2012;14:1-6.\u003c/li\u003e\n\u003cli\u003eGrundtman C, Tham E, Ulfgren AK, Lundberg IE. Vascular endothelial growth factor is highly expressed in muscle tissue of patients with polymyositis and patients with dermatomyositis. Arthritis Rheum. 2008;58(10):3224-3238.\u003c/li\u003e\n\u003cli\u003eNeumann J, Bilzer T. Evidence for MHC I-restricted CD8+ T-cell-mediated immunopathology in canine masticatory muscle myositis and polymyositis. Muscle Nerve. 2006;33(2):215-224.\u003c/li\u003e\n\u003cli\u003eYang SH, Chang C, Lian ZX. Polymyositis and dermatomyositis - challenges in diagnosis and management. J Transl Autoimmun. 2019;2:100018.\u003c/li\u003e\n\u003cli\u003eFerrara N. Vascular endothelial growth factor: basic science and clinical progress. Endocr Rev. 2004;25(4):581-611.\u003c/li\u003e\n\u003cli\u003eLundberg IE. Vascular endothelial growth factor (VEGF) expression in muscle tissue and the effect of corticosteroid therapy in patients with poly- and dermatomyositis. Arthritis Res Ther. 2002;4(Suppl 1):12.\u003c/li\u003e\n\u003cli\u003eTauro A, Addicott D, Foale RD, Bowman C, Hahn C, et al. Clinical features of idiopathic inflammatory polymyopathy in the Hungarian Vizsla. BMC Vet Res. 2015;11(1):1-13.\u003c/li\u003e\n\u003cli\u003eForeman M, Cherubini GB. Dexamethasone can be safely and effectively used for treatment of masticatory muscle myositis in dogs. Top Companion Anim Med. 2021;44:100538.\u003c/li\u003e\n\u003cli\u003eOddis CV. Update on the pharmacological treatment of adult myositis. J Intern Med. 2016;280(1):63-74.\u003c/li\u003e\n\u003cli\u003eAlijotas J, Barquinero J, Ordi J, Vilardell M. Polymyositis and cyclosporin A. Ann Rheum Dis. 1990;49(1):66.\u003c/li\u003e\n\u003cli\u003eVan der Meer S, Imhof JW, Borleffs JC. Cyclosporin for polymyositis. Ann Rheum Dis. 1986;45(7):612.\u003c/li\u003e\n\u003cli\u003eChandra BS, Prabavathy AA, Vijayalakshmi P, Selvi D, Rajkumar K, et al. Polymyositis in a Doberman bitch. Indian J Anim Hlth. 2017;56(2):279-282.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-veterinary-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [BMC Veterinary Research](http://bmcvetres.biomedcentral.com/)","snPcode":"12917","submissionUrl":"https://submission.nature.com/new-submission/12917/3?","title":"BMC Veterinary Research","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Dog, Polymyositis, Immune-mediated, MRI","lastPublishedDoi":"10.21203/rs.3.rs-4785771/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4785771/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e1.\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Background\u003c/p\u003e\n\u003cp\u003eInflammatory myopathy is generally categorized into generalized inflammatory myopathies (gIM), which affect muscles throughout the body, and focal inflammatory myopathies (fIM), which are localized to specific muscles or muscle groups. This report details a case of immune-mediated polymyositis in a dog, successfully diagnosed using MRI and IHC and managed with immunosuppressive therapy.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e2.\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Case presentation\u003c/p\u003e\n\u003cp\u003eA 5-year-old castrated male Poodle was admitted to a hospital presenting with lethargy and exercise intolerance. Biochemical analysis revealed significantly elevated serum levels of aspartate aminotransferase (AST) and creatine kinase (CK). Physical examination showed muscle atrophy in the hind legs, but further orthopedic and neurological examinations identified no additional abnormalities. MRI demonstrated hyperintense and heterogeneous signal changes across the muscles, including contrast enhancement, suggesting polymyositis. This diagnosis was confirmed through histopathological examination, which revealed inflammatory lesions with fibrous tissue proliferation within the muscle tissue.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e3.\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; Conclusions\u003c/p\u003e\n\u003cp\u003eThe dog was diagnosed with immune-mediated polymyositis and treatment was initiated with prednisolone (Solondo\u003csup\u003e®\u003c/sup\u003e, Yuhan Pharmaceuticals) at 1 mg/kg twice daily and azathioprine (Immuthera\u003csup\u003e®\u003c/sup\u003e, Celltrion Pharmaceuticals) at 2 mg/kg once daily. Following the administration of these immunosuppressive agents, CK levels returned to normal, and the dog’s exercise intolerance and lethargy resolved. The thickness of the hind legs also increased progressively. The dog has maintained an improved condition under continued immunosuppressive therapy for four months. This case highlights the critical role of MRI and immunohistochemistry in diagnosing immune-mediated polymyositis, demonstrating their superiority over conventional electromyography (EMG) in this context.\u003c/p\u003e","manuscriptTitle":"A Case of Canine Immune-Mediated Polymyositis: Update of the diagnosis and clinical evaluation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-26 11:34:40","doi":"10.21203/rs.3.rs-4785771/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-08-07T10:06:18+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-08-03T15:42:08+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-08-02T19:59:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"327556697643351790958183738230816116554","date":"2024-07-31T18:21:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"322083009466543450678434823291739479787","date":"2024-07-30T23:56:38+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-07-30T04:36:01+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-07-30T01:52:41+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-07-30T01:34:04+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-07-23T09:04:59+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Veterinary Research","date":"2024-07-23T05:22:41+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-veterinary-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [BMC Veterinary Research](http://bmcvetres.biomedcentral.com/)","snPcode":"12917","submissionUrl":"https://submission.nature.com/new-submission/12917/3?","title":"BMC Veterinary Research","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ff3c46da-ade2-428b-82e1-7118c5d036d1","owner":[],"postedDate":"August 26th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-12-16T16:01:03+00:00","versionOfRecord":{"articleIdentity":"rs-4785771","link":"https://doi.org/10.1186/s12917-024-04356-6","journal":{"identity":"bmc-veterinary-research","isVorOnly":false,"title":"BMC Veterinary Research"},"publishedOn":"2024-12-10 15:57:34","publishedOnDateReadable":"December 10th, 2024"},"versionCreatedAt":"2024-08-26 11:34:40","video":"","vorDoi":"10.1186/s12917-024-04356-6","vorDoiUrl":"https://doi.org/10.1186/s12917-024-04356-6","workflowStages":[]},"version":"v1","identity":"rs-4785771","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4785771","identity":"rs-4785771","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}