International Workshop on Inclusion Body Myositis held at the Institute of Myology, Paris, on 29 May 2009.

This 1-day workshop was organized by Olivier Benveniste and David Hilton-Jones and assembled 20 clinicians, pathologists and researchers (see the list of participants) from four countries (UK, USA, Austria, France). This workshop followed one held in London 1 year earlier with some common participants [1] in order to reinforce a collaborative interface between several international groups actively investigating the clinical features, pathogenesis and treatment of sporadic inclusion body myositis (sIBM). To date, all drugs tested in randomized clinical trials (RCT) appear to be comparable to placebo [2–9]. Nevertheless, new molecules are emerging [10,11]. The assessment of potential new treatments is hampered by difficulties in the design of trials, relating in part to the slowly progressive nature of the disorder and uncertainties about the natural history, and the low incidence and prevalence of the disease. Evaluation of required sample size for future sIBM trials has been calculated from the results of two studies using two doses (30 and 60 lg/weekly) of bIFN (without any difference in strength between the 57 placebo or IFN treated patients) [2,3]. For a two-arm, 6-month therapeutic intervention, aiming to show arrest of disease progression, it would require 208 subjects per group [2,3]. The enrolment of such a number of patients would be achievable only in a collaborative international multicentre study. Treatments that slow, rather than arrest, progression would need larger numbers, and also longer studies with associated increased costs. The first part of the meeting reviewed the currently widely used diagnostic criteria proposed by RC Griggs et al. [12]. The need for consensus with respect to pathological assessment of muscle biopsy specimens, particularly immunohistochemistry, was agreed. The second part of the meeting was devoted to defining the outcome measures for such trials, and finally we explored the possibilities for international RCTs.