In 2003 van der Meulen and colleagues published a paper suggesting that PM is an overdiagnosed entity [21]. On the basis of the immunopathological findings discussed above, suggesting a clear distinction between DM and PM, van der Meulen required the presence of endomysial mononuclear cells surrounding, and preferably invading, non-necrotic fibres to make a diagnosis of definite PM. If the inflammatory infiltrate was not endomysial,

but perimysial/perivascular, they classified the patient as having “unspecified myositis”. They also click here excluded the diagnosis of PM if there was an associated collagen-vascular disease. Several groups argued that it was not that PM was overdiagnosed, but that the authors were guilty of over-adherence to unvalidated pathological diagnostic criteria [34]. As already noted, it is certainly not uncommon in everyday practice to see biopsies lacking specific changes. The biopsy appearance has to be interpreted along with the clinical picture and other laboratory findings and it is not surprising that not every laboratory abnormality will be present in every case. In most instants it is

possible to categorise the patient as having DM, PM or myositis associated with a CTD, and in the latter group it may be semantic as to whether to call it myositis or PM. A major reason for attempting classification is to ensure homogeneous groups for clinical trials. With trial design in mind a European Selleckchem PD332991 Neuromuscular Centre Workshop in 2003 proposed revised diagnostic criteria and overall classification which drew upon the developments, described above, unless since the 1975 Bohan and Peter classification [35]. Five major groups representing the IIM were proposed: • 1: inclusion-body myositis; PM and DM could be further categorised as definite or probable, depending on the presence of specific

clinical and laboratory criteria. Subcategories of DM included DM sine dermatitis and amyopathic DM–the former on the basis of the characteristic immunopathological muscle biopsy findings of DM, but in the absence of a rash, and the latter with a typical rash and skin biopsy showing appropriate immunopathological findings, but no clinical or pathological evidence of muscle involvement. As discussed above, non-specific myositis depends upon the presence of inflammatory cells, but not surrounding and invading non-necrotic fibres. Immune-mediated necrotising myopathies behave clinically like other myositides in terms of pattern of muscle involvement, progression and response to immunosuppression, and the biopsy shows necrotic fibres but in the absence of inflammatory infiltrates. Groups 2, 3, 4 and 5 may each be associated with features of connective tissue disease, and each group may also be associated with neoplasia.