Background/Purpose:  several data are available about the use of IvIg in the treatment of idiopathic inflammatory myopathies (IIM), but the results derive from small cohorts. The aim of our study is to evaluate the efficacy of IvIg in a monocentric cohort of patients with IIMs.

Methods:  retrospective study of IIM pts treated in our unit with IvIg in the last 5 years (2gr/kg/month). We evaluated ESR, CRP, creatine kinase CK; muscle strength (manual muscle test 8 – MMT8), clinical symptoms (dysphagia, dyspnea, loss of strength) at the baseline, after 6 months and at the last follow-up. We analyzed indications to treatment, major organ involvement, previous therapies, adverse events (AE).

Results:  50 pts were enrolled (17 M, 33 F), 25 PM, 24 DM, 1 IBM; 9 (3 PM, 6 DM) were affected by paraneoplastic disease. Mean disease duration was 23.7±47 months. Indications to the treatment were: loss of strenght (all patients), dysphagia (19), lung involvement (6), DM rash (18), arthritis (2) and fever (1). IvIg were chosen for refractory disease (32 pts), neoplasia (9), recurrent infections (8), pregnancy (1). Previous treatment included corticosteroids in all patients (mean cumulative dose 5.4±7.0 grams), MTX in 17, CSA in 6, rituximab in 3, CYC in 5, AZA in 4, MMF in 5. After 6 months muscular strength improved in 26/41 patients and no patient worsen. Mean CK levels were significantly reduced from 1647±2140UI/ml to 368±662UI/ml (p=0.023). Mean MMT8 values increased from 56.0 to 61.6 (p<0.001). DM skin rash improved in 12/18 patients, dysphagia in 16/19, dyspnea in 7/10, arthritis in 2/2. At last observation 21 patients were still in IvIg treatment; patients received a mean of 29 infusions (min 1, max 164). 41 patients are still in follow up (9 died for myositis related causes); the mean follow-up duration is 66 months. Seven patients presented AE but only 2 pts stopped the treatment (1 arrhythmia, 1 heart failure). 47 patients maintained improvement of the muscular strength, 1 pt presented DM skin rash, dysphagia was still present in 12 pts but less severe compared to the baseline. MMT8 globally improved (p<0.001) and CK reduced (p<0.001).

Conclusion:  IvIg is an expensive treatment, but our data confirmed their efficacy and safety particularly in refractory IIM patients. Muscular strength, dysphagia, arthritis and DM skin rash are the most responsive manifestations, particularly during the first 6 months of the therapy. On the light of these data, new perspective trials on the therapeutic approach of IIM are needed, to evaluate the best timing of IvIg treatment in IIM.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/intravenous-immunoglobulins-in-the-treatment-of-idiophatic-inflammatory-myopathies-where-do-we-stand/