Inflammatory myopathies and overlap syndromes: Update on histological and serological profile




Abstract


The term ‘inflammatory myopathies’ (IMs) comprise a group of muscle diseases formed by four main categories known as polymyositis (PM), dermatomyositis (DM), inclusion body myositis (IBM) and immune-mediated necrotizing myopathy (IMNM). Due to the increasing evidence of IMs over the course of different autoimmune diseases, the overlap myositis (OM) has been recently recognized as a possible stand-alone entity. IMs are characterized by a wide spectrum of autoantibodies, and the panel of myositis-associated autoantibodies (MAA) has dramatically increased over the last years giving the clinicians a further crucial support to differentiate the different types of myositis. This study aims to collect the most relevant evidence published up to date on the most commonly described OM with a particular emphasis on their histological aspects and also serological features.


List of abbreviations


ARS


aminoacyl-tRNAsynthetase


CK


creatine kinase


COX


histochemical cytochrome C oxidase


DM


dermatomyositis


ENMC


European Neuromuscular Centre Criteria


ESR


erythrocytes sedimentation rate


IBM


inclusion body myositis


IHC


immunohistochemical


ILD


interstitial lung disease


IMs


inflammatory myopathies


IMNM


immune-mediated necrotizing myopathy


MAA


myositis-associated antibodies


MAC


membrane attack complex


MCTD


mixed connective tissue disease


MHC I


major histocompatibility complex class I


MRC


Medic Research Council


MRI


magnetic resonance imaging


MSA


myositis specific antibodies


NIMs


non-inflammatory myopathies


NIMNM


non-immune-mediated necrotizing myopathy


OM


overlap myositis


PM


polymyositis


RA


rheumatoid arthritis


SERD


disproportionately elevated ESR


SLE


systemic lupus erythematosus


SS


systemic sclerosis


SjS


Sjögren’s syndrome


SRP


signal recognition pattern


Introduction


Inflammatory muscle diseases comprise a heterogeneous group of myopathies that may be classified into four main categories based on clinical and histological features: polymyositis (PM), dermatomyositis (DM), inclusion body myositis (IBM) and immune-mediated necrotizing myopathy (IMNM). The overlap myositis (OM), wherein polyarthritis, Raynaud’s phenomenon and interstitial lung disease (ILD) are more commonly observed, has been recently recognized as a possible stand-alone category of inflammatory myopathies (IMs). This study aims to update on the diagnostic and classification criteria currently used for myositis as well as to describe in detail both histological and serological features of OM. Thus, we focused on the description of the most common forms of OM in the presence of the following autoimmune diseases: systemic sclerosis (SS), systemic lupus erythematosus (SLE), Sjögren’s syndrome (SjS) and rheumatoid arthritis (RA).




Myositis classification criteria


In the past years, several classification and diagnostic criteria ( Tables 1, 2 and 3 a/b ) for IMs have been proposed; however, to date, a unanimous consensus has not been achieved. Those proposed by Bohan and Peter in 1975 still represent the most commonly used criteria for inclusion in clinical trials. However, those criteria have been criticized for different reasons. First, they do not mention IBM because they predate its recognition as a separate condition; second, a loose definition of OM is given. Because of this, such criteria provide an over-diagnosis of PM causing, in turn, a possible patient’s selection bias both in case series studies and in clinical trials.



Table 1

Bohan and Peter diagnostic criteria for IMs.































Bohan and Peter 1975


  • 1)

    Symmetrical weakness, usually progressive, of the limb-girdle muscles and anterior neck flexors, progressing over weeks to months, with or without dysphagia or respiratory muscle involvement



  • 2)

    Muscle biopsy evidence of myositis (necrosis of type I and type II muscle fibres, phagocytosis, degeneration and regeneration of myofibres with variation in myofibre size, endomysial, perimysial, perivascular or interstitial mononuclear cells)



  • 3)

    Elevation of serum levels of muscle-associated enzymes (CK, Aldolase, LD, Transaminases)



  • 4)

    Electromyographic triad of myopathy (short, small, low-amplitude polyphasic motor unit potentials, fibrillation potentials, even at rest, bizarre high-frequency repetitive discharges)



  • 5)

    Characteristic rashes of dermatomyositis

Diagnosis PM DM
Definite All first 4 Rash +3 others
Probable 3 of first 4 Rash +2 others
Possible 2 of the first 4 Rash +1 other

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Nov 10, 2017 | Posted by in RHEUMATOLOGY | Comments Off on Inflammatory myopathies and overlap syndromes: Update on histological and serological profile

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