The study of idiopathic inflammatory myopathies (IIMs) is acquiring growing importance among systemic autoimmune diseases and every year several articles are published about this group of diseases. Despite this growing interest, the management of IIMs is still critical due to the relative rarity of the condition. The availability of upto-date knowledge of the evidence on this subject is essential to correctly understand this condition and provide the best care for the patients. The purpose of this review is to provide an overview of the most relevant literature contributions published in the last year.

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Muscular involvement is common during systemic vasculitides, such as polyarteritis nodosa. However, in rare cases, muscular involvement can be the only clinically evident feature of the disease. The clinical pattern of isolated muscular vasculitis may mimic several other inflammatory muscle disorders, such as idiopathic inflammatory myositis, and may represent a challenge in differential diagnosis. Herewith, we present two clinical cases as examples of peculiar clinical and histopathological characteristics of isolated muscular vasculitis. Our patients were successfully treated with steroids and immunosuppressive agents. Moreover, we provide a review of the recent existing medical literature. Our cases suggest the importance of performing muscle biopsy in patients with muscular symptoms to guide the diagnosis and the treatment.

Idiopathic inflammatory myopathies (IIM) are a rare disease; so far standardized therapy has not been adequately defined by national or international guidelines or recommendations. Corticosteroids are the mainstay of treatment, but these drugs are burdened by several side effects. Thus, additional treatment based on immunosuppressive agents, especially azathioprine, methotrexate, mycophenolate mofetil and cyclosporine, is often needed. This combinate approach both improves the disease response and allows reduction of the dosage of corticosteroids, decreasing the risk of steroid-related long-term complications. Biological agents, particularly B cell depleting agent, are emergent therapeutic tools for refractory cases. Notably, drugs currently used for the therapy of IIM or other rheumatologic and non-rheumatologic conditions can induce myopathy. Drug-induced myopathies represent a considerable part of the complex topic of muscular disorders and should be always considered in the usual diagnostic work-up of a subject with muscle disease. Several mechanisms have been advocated to explain muscular damage induced by a number of drugs and, although a recovery after drug removal is usually observed, severe or persistent myopathy may be observed following the administration of some drugs, particularly in subjects with genetic predisposition. In this review the traditional and novel therapeutic approaches for patients with IIM, particularly biologics, will be discussed and an overview on drug-induced myopathies will also be provided.

Rituximab (RTX), a chimeric monoclonal antibody targeted against CD20, has been used to treat refractory inflammatory myopathies (IIM). The primary objective of this study was to retrospectively assess the efficacy of RTX in reducing disease activity in patients with IIM refractory to conventional therapy. Secondary aim was the evaluation of adverse events (AE) during the treatment period. We examined 26 patients with a diagnosis of IIM, referred to our Rheumatology Unit and treated with RTX for active refractory disease. Patients were treated with RTX 1000 mg i.v., twice, with a 2-week interval. RTX treatment was associated with a significant reduction of creatine kinase (p=0.001) after six months compared to the baseline, an improved muscular strength measured with MMT8 (p<0.001) and a reduction of the extramuscular activity of the disease measured with MYOACT (p<0.001). In particular, RTX improved DM skin rash, arthritis and pulmonary manifestations. Autoantibody positivity (in particular antisynthetase, anti- SRP and antiRo/SSA), and a disease duration <36 months at the moment of the treatment are associated with a better response rate. Treatment with RTX was also associated with a reduction of the mean daily dose of steroids needed to control disease activity (p=0.002). Our results have confirmed that RTX is efficacious in the treatment of refractory IIM. Ad hoc controlled trials are needed to better clarify the specific subset of patients who may better respond to the treatment and the optimal therapeutic schedule.