Immunoglobulin Treatment inPolymyositis and Dermatomyositis

Polymyositis (PM) and dermatomyositis (DM) are systemic autoimmune diseases of unknown aetiology in which the skeletal muscles are the main targets. Despite the improvement obtained in the last years with new therapeutic options, their prognosis remains poor, with higher rates of morbidity and mortality. Due to the rarity of the disease, few well-designed studies have been published and, to the best of our knowledge, only five randomised controlled trials. The low incidence of the disease, the characteristic relapsing/remitting or chronic and persistently active course, the lack of agreed standardised criteria for diagnosis and for assessment of disease activity makes difficult to carry and to compare studies. Among the treatment options, the use of intravenous immunoglobulin (IVIg) is still matter of debate. In this chapter we describe the use of IVIg in PM and DM, revising the literature and reporting our experience. We analyse our series of 74 subjects with PM or DM diagnosed according to the Bohan and Peter criteria. Usually, IVIg is given in case of refractory or relapsed disease, steroid resistance or dependency. In a previous revision of our data related to 63 patients, we documented that subjects treated with IVIg achieve a clinical and functional remission in a high percentage of cases, that is maintained at long follow-up period (a mean of five years), as compared to control group. The revision of the literature and our data confirm that IVIg is effective alone or as add on therapy in the treatment of inflammatory myopathies, even in refractory or relapsed disease. Most of the patients with PM or DM receive an immunosuppressant such as cyclosporine A (CSA) or mycophenolate mofetil (MMF). We want to verify if the use of IVIg as add-on treatment with CSA or MMF could improve the outcome or could reduce the rate of side effects that are usually linked to the immunosuppressant. We thus revise the literature and our data related to the use of CSA and MMF in PM or DM. The subcutaneous administration (SCIg) could be considered as an alternative to IVIg. In primary immunodeficiency, SCIg has been demonstrated to be linked to a lower incidence of adverse reactions, with reliable efficacy and improvement of the quality of life of treated subjects. We have been the first to publish about a series of seven patients with autoimmune myopathies treated with SCIg. We could document the feasibility and the good tolerance of SCIg, with relevant improvement of the clinical and laboratory features. We here present data related to a larger series. Finally, we review the data related to the mechanisms of action of immunoglobulin administration in autoimmune mediated diseases, in particular underlying the different proposed mechanism of IVIg and SCIg.