Objective: Polymyositis is a rare inflammatory muscular disease of unknown cause. Corticosteroids and immunosuppressive drugs are the first choice of therapy but are not always effective and may cause serious side effects. Many studies have shown that polyvalent intravenous immunoglobulin (IVIG) may be of interest for the treatment of dermatomyositis. We carried out an open, prospective study to evaluate the efficacy of IVIG in subjects with polymyositis that was refractory to traditional treatments, and we evaluated the benefits of this therapy over a long-term period of followup.
Methods: Thirty-five adult white patients (20 female, 15 male, mean age 43.5 years [SD 16.8]) with chronic, refractory polymyositis were treated with high doses of IVIG, after the patients had received the following traditional treatments: prednisone (n = 35), methotrexate (n = 24), azathioprine (n = 13), cyclophosphamide (n = 4), cyclosporine (n = 7), chlorambucil (n = 1), plasmapheresis (n = 8), lymphopheresis (n = 1), and total body irradiation (n = 1). There had been no changes in the patients' treatment in the 2 months before the initiation of IVIG therapy, and doses were not increased during IVIG treatment. We used preparations of polyvalent human IVIG with increased concentrations of intact IgG. The patients received 1 gm/kg/day for 2 consecutive days per month. The mean course of treatment was 4-6 months. The clinical assessment involved the evaluation of proximal muscle power, muscle disability scale score, and esophageal disorders. The biochemical evaluations carried out before each treatment period were compared by Student's t-test and nonparametric Wilcoxon test. Results were considered to be significant at P = 0.05.
Results: In the short-term, significant clinical improvement was noted in 25 of the 35 patients (71.4%). Mean muscle power was estimated before and after IVIG therapy and was found to be significantly improved (P < 0.01). All patients had a significant biochemical response. Mean creatine kinase levels during IVIG therapy decreased significantly before the fourth IVIG perfusion (P < 0.01). Side effects, usually minor, were noted in 6 patients. This benefit allowed the initial prednisone dose to be reduced by >50% in all patients. The mean (+/- SD) followup time for the 25 patients who responded favorably to IVIG treatment was 51.4 +/- 13.1 months. Twelve of these 25 patients remained in full remission following their initial course of IVIG, resulting in complete stoppage of medication in 5 patients or low doses of steroids in 7 patients. The condition of 6 patients remained improved and no other drugs were prescribed, but the patients remained dependent on IVIG infusions. Seven of the 25 patients who responded well to IVIG treatment relapsed at an average of 17.1 months (range 4-23 months) after the discontinuation of IVIG.
Conclusion: IVIG is an interesting therapy for the treatment of polymyositis, with results showing that the condition of approximately 70% of the patients tested improved. After the discontinuation of the IVIG therapy, the efficacy remained stable in 50% of the patients, with a followup of over 3 years.