The need for further international collaboration between interested specialists was emphasised and the goals of the International Myositis Assessment and Clinical Studies (IMACS) group noted [37]. I am told that in the 1970s the rheumatologists at a large London teaching hospital were wont to use the abbreviation SSOM–some sort of myositis. I assume that this was an honest attempt to indicate ignorance about cause and that they felt more comfortable “lumping” cases with many common features together, rather than “splitting” up into

subcategories when there was no clear rationale to do so. Are we now any the wiser? I think that the answer is definitely yes, but note again the wise words of my colleague who selleck warned against rigid definitions in that they may lead us to assume we know more than we Ipatasertib research buy do. The major development relates to our increased understanding of the immunopathogenesis of

DM and PM, although it is clear that we do not understand all of the relevant mechanisms. It is salutary to remember why we are trying to achieve a system of classification, and how we might go about doing so. The critical relationship between establishing diagnostic criteria and any system of classification has been emphasised. The main benefits of classification are in aiding the diagnostic

approach, defining specific subgroups that have a similar natural history and response to treatment, and leading on from that are helpful for epidemiological studies. Arguably, definitive classification depends upon identifying the specific cause of each disorder. A comparison can be made with limb-girdle muscular dystrophy. In the 1950s we were able to define LGMD by clinical features and certain histological features. We could see that some patients had particular associated features whereas others did not–e.g. cardiomyopathy or early ventilatory muscle involvement. Now we can define individual subtypes at a many molecular level and note which are associated with such complications. For the myositides we are somewhere between these two stages. Box 4 is essentially a synthesis of previous classifications that is intended to be useful clinically–in other words, most patients can, on the basis of clinical and laboratory features, be placed in a specific category. The first part of Box 4 lists conditions with either a known cause (rather few) or those in which myositis is associated with another definable entity, although the pathogenic relationship between the two may be uncertain. The second part includes what are frequently referred to as the IIM.