Background/Purpose:

Dermatomyositis (DM) and polymyositis (PM) are idiopathic inflammatory myopathies characterized by weakness and inflammation of the muscles. First line therapy typically involves high dose systemic steroids to establish disease control along with steroid sparing agents to minimize steroid induced morbidities. Other immunosuppressive agents are typically initiated as an adjunct to systemic steroids, with scarce evidence supporting use of various agents in the clinical context. Intravenous immunoglobulin therapy (IVIG) in particular has demonstrated evidence in severe refractory disease. Our study aims to investigate the efficacy of IVIG in the treatment of various clinical manifestations of inflammatory myopathies.

Methods: A retrospective chart review was performed on patients identified through the Sunquest Laboratory Information System who had received IVIG for the treatment of DM or PM between January 1^st, 2012 to January 1^st, 2018 at the University of Alberta Hospital. Data extracted included patient’s age at initiation of treatment, sex, duration of treatment, presenting symptoms (weakness, myalgias, skin rashes, calcinosis, dysphagia and interstitial lung disease [ILD]) and outcome of treatment.

Results: A total of 46 DM and 19 PM patients were identified. Median age of treatment onset was 54 (interquartile range [QR], 40 – 64) years, with 49 (75%) female patients. The median duration of treatment was 13 (QR, 3 – 37) months. Fifty-six of sixty-five (86%) patients had weakness, 7/65 (11%) patients had myalgias, 40/65 (62%) patients had rashes, 5/65 (8%) had calcinosis, 16/65 (25%) had dysphagia and 6/65 (9%) had ILD. Initiation of IVIG improved symptoms of weakness for 41/56 (73%) patients, myalgias for 6/7 (86%) patients, rashes for 33/40 (83%) patients, calcinosis for 0/5 (0%) patients and dysphagia for 12/16 (75%) patients. IVIG improved the ILD for 1/6 (17%) patients and the remaining 5/6 (83%) patients did not demonstrate progression of their ILD.

Conclusion: This large retrospective cohort study indicates the utility of IVIG in the management of idiopathic inflammatory myopathies. The results of our study suggest that a course of IVIG at 2 g/kg per month administered over 2-5 days is effective in treating refractory inflammatory myopathies and particularly effective in treating symptoms of weakness, myalgias, rashes and dysphagia. IVIG however appears generally ineffective in treating calcinosis as well as ILD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/management-of-idiopathic-inflammatory-myopathies-using-intravenous-immunoglobulin-therapy-a-retrospective-cohort-study/