Polymyositis
Polymyositis (PM) is an idiopathic inflammatory myopathy characterized by muscle weakness and inflammation. Treatment involves glucocorticoids, typically prednisolone or methylprednisolone, followed by tapering. Glucocorticoid-sparing agents like azathioprine or methotrexate may be considered if needed. Severe cases may benefit from intravenous immune globulin (IVIG). Physical therapy and dietary precautions are also important.
2024-01-08 15:38:30 - Editor
Polymyositis (PM): Overview and Diagnostic Confirmation
Polymyositis (PM) is an idiopathic inflammatory myopathy, characterised by the shared features of progressive proximal skeletal muscle weakness and evidence of inflammation in muscles. Muscle biopsy, electromyography are essential to confirm the diagnosis. (1, 2)Polymyositis (PM) is an idiopathic inflammatory myopathy, characterised by the shared features of progressive proximal skeletal muscle weakness and evidence of inflammation in muscles. Muscle biopsy, electromyography are essential to confirm the diagnosis. (1, 2)
Treatment Goals and Initial Therapy for PM
The goals of treatment are to improve muscle strength and to avoid the development of extramuscular complications. Glucocorticoids are the cornerstone of initial therapy for PM. (3)
Glucocorticoid Administration and Tapering
Glucocorticoids are usually initiated as either prednisolone (1 mg/kg per day for approximately 6 weeks) or for ill patients; methylprednisolone (1000 mg per day for three days, followed by prednisolone tapering doses, based on clinical improvement and improvement in muscle enzymes, for approximately 6 weeks). Then, steroid tapering is required over about 26 weeks to reach a daily dose of 5 mg depending on response improvement. Most patients discontinue glucocorticoids at 9 to 12 months. Also, patients require prophylaxis against osteoporosis and opportunistic infections with trimethoprim/ sulfamethoxazole (TMP/SMZ) 160/800 mg while on steroids. (4, 5, 6)
Considerations in Case of Glucocorticoid Failure
In the setting of apparent failure to glucocorticoids, three possibilities should be reviewed including an alternative diagnosis, such as, muscular dystrophy, glucocorticoid- induced myopathy, or an unrecognized malignancy associated with myositis. Once the above 3 possibilities are ruled out, then, the addition of a glucocorticoid- sparing agent has to be considered. Glucocorticoid- sparing agents (for about 6 months based on patient's improvement condition) include azathioprine (starting at 50 mg/day), or methotrexate (starting at 15mg/week). (7, 8)
Management of Severe Weakness and Dysphagia
Also, patients with severe life- threatening weakness or severe dysphagia are at risk for aspiration and may benefit from the addition of intravenous immune globulin (IVIG) to initial treatment with glucocorticoids. (9)
Non-Pharmacological Measures in PM
Non- pharmacological measures in PM include physical therapy including strength, isometric and resistive exercise, speech therapy. Precautions include elevation of the head of the bed, semi-thick diets. A nasopharyngeal or gastric feeding tube may be required in patients with esophogeal dysfunction. (10)
References
1- Johnson NE, Arnold WD, Hebert D, Gwathmey K, Dimachkie MM, Barohn RJ, et al. Disease course and therapeutic approach in dermatomyositis: a four-center retrospective study of 100 patients. Neuromuscul Disord. 2015;25:625–31.
2- Joffe MM, Love LA, Leff RL, Fraser DD, Targoff IN, Hicks JE, et al. Drug therapy of the idiopathic inflammatory myopathies: predictors of response to prednisone, azathioprine, and methotrexate and a comparison of their efficacy. Am J Med. 1993;94:379–87.
3- Oddis CV. Update on the pharmacological treatment of adult myositis. J Intern Med. 2016;280:63–74.
4- Cavagna L, Monti S, Caporali R, Gatto M, Iaccarino L, Doria A. How I treat idiopathic patients with inflammatory myopathies in the clinical practice. Autoimmun Rev. 2017;16:999–1007
5- Raghu P, Manadan AM, Schmukler J, Mathur T, Block JA. Pulse dose methylprednisolone therapy for adult idiopathic inflammatory myopathy. Am J Ther. 2015;22:244–7.
6-van der Goes MC, Jacobs JWG, Boers M, Andrews T, Blom-Bakkers MAM, Buttgereit F, et al. Monitoring adverse events of low-dose glucocorticoid therapy: EULAR recommendations for clinical trials and daily practice. Ann Rheum Dis. 2010;69:1913–9.
7- Hoes JN, Jacobs JWG, Boers M, Boumpas D, Buttgereit F, Caeyers N, et al. EULAR evidence-based recommendations on the management of systemic glucocorticoid therapy in rheumatic diseases. Ann Rheum Dis. 2007;66:1560–7
8- Miller J, Walsh Y, Saminanden S, Lecky B, Winer JB. Randomised double blind trial of methotrexate and steroids compared with azathioprine and steroids in the treatment of idiopathic inflammatory myopathy. J Neurol Sci. 2002;199:S53.
9- Iaccarino L, Bartoloni E, Gerli R, Alunno A, Barsotti S, Cafaro G, et al.Drugs in induction and treatment of idiopathic inflammatory myopathies. Auto Immun Highlights. 2014;5:95–100.
10-Alexanderson H, Lundberg IE. The role of exercise in the rehabilitation of idiopathic inflammatory myopathies. Curr Opin Rheumatol 2005; 17:164.