O.16 Morphological and molecular heterogeneity in autoimmune necrotizing myopathies

Abstract

Autoimmune necrotizing myopathies (ANM) represent a well-recognized entity among the so-called idiopathic inflammatory myopathies (IIMs), which also comprise dermatomyositis (DM), polymyositis (PM), sporadic inclusion body myositis (sIBM) and non-specific myositis. The diagnosis of these IIMs is established on the basis of specific clinical symptoms, results derived from muscle biopsy and ancillary data, such as creatine kinase (CK) levels, electromyography (EMG) and modern imaging techniques. Myositis-associated and myositis-specific autoantibodies play an important role and may prove to be clues for understanding details of the pathogenesis of these conditions, which to date remain largely unknown. ANMs probably represent a heterogeneous group of diseases all of which are characterized by the striking presence of necrotic fibres on muscle biopsy. However, additional morphological features as well as certain autoantibodies (e.g. SRP or HMGCR auto-antibodies) may be helpful to define subgroups of ANM. Subclassification of ANMs and definition of specific syndromes with precise and characteristic immunological features is a subject of intense research, especially since clinical trials with anti-inflammatory agents or so called ’biologicals’ should follow universally defined and accepted criteria. We present molecular and morphological data of subgroups within the spectrum of autoimmune necrotizing myopathies.