MYOSITIS

[Pages:40]MYOSITIS

A physician's guide to the EJ=II=PKNUIUKL=PDEAO

contents

TABLE OF CONTENTS

Myositis basics .................................................. 1 0ECJO=J@OUILPKIO ........................................ 3 Causes ................................................................ 7 -NKCJKOEO.......................................................... 11 Affected populations....................................... 15 Diagnosis.......................................................... 17 1NA=PIAJP......................................................... 25 /ABANAJ?AO........................................................ 31

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PHYSICIAN'S GUIDE TO MYOSITIS

*UKOEPEO EO = PANI QOA@ PK NALNAOAJP PDA E@EKL=PDE? EJ=Imatory myopathies, rare diseases that are predominantly immune-mediated and cause skeletal muscle weakness. If HABP QJPNA=PA@ IUKOEPEO ?=J ?=QOA OECJEl?=JP IKN>E@EPU =J@ even death.

WHAT IS MYOSITIS?

1DASKN@IUKOEPEOHEPAN=HHUIA=JOEJ=II=PEKJKBIQO?HA&J a clinical context, however, the term is used to identify the E@EKL=PDE?EJ=II=PKNUIUKL=PDEAO N=NA@EOA=OAOKBOGAHAP=H muscle (1,2). These diseases are polymyositis, dermatomyoOEPEO FQRAJEHA @ANI=PKIUKOEPEO =J@ EJ?HQOEKJ >K@U IUKOEPEO Polymyositis, dermatomyositis, and juvenile dermatomyositis =NA=QPKEIIQJA@EOKN@ANO SDANA=OEJ?HQOEKJ>K@UIUKOEPEO

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D=OBA=PQNAOKB>KPD=QPKEIIQJEPU=J@IQO?HAl>AN@ACAJANation (3). These heterogeneous myopathies are characterized >UIQO?HASA=GJAOOPD=PEOQOQ=HHULNKTEI=H=J@OUIIAPNE? =J@JKJOQLLQN=PERAEJ=II=PEKJEJOGAHAP=HIQO?HA

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SIGNS AND SYMPTOMS

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The cardinal feature of polymyositis, symmetric weakness of proximal muscles (pelvic and shoulder girdle musculature) deRAHKLOKRANSAAGOPKIKJPDO-=PEAJPOD=RA@EBl?QHPUEJNEOEJCBNKI=?D=EN ?HEI>EJCOP=ENO KNLANBKNIEJC=?PEREPEAOPD=P NAMQENAPDAEND=J@OPK>AN=EOA@KRANPDAENDA=@O&JL=PEAJPO with more extensive disease, distal weakness can occur, JA?GATKNSA=GJAOO?=JHA=@PKDA=@@NKL LD=NUJCA=HIQOcle weakness can result in dysphagia and/or dysphonia, and diaphragm involvement can cause respiratory compromise. *U=HCE= I=U KN I=U JKP >A NALKNPA@ ,J LDUOE?=H AT=IEJ=PEKJ lTA@SA=GJAOOEOBKQJ@EJ@AHPKE@O >E?ALO PNE?ALO DEL ATKNO MQ=@NE?ALO =J@D=IOPNEJCO

,PDAN BA=PQNAO PD=P I=U >A LNAOAJP EJ?HQ@A BARAN @UOLJA= (due to interstitial lung disease, aspiration, diaphragm weakness, or cardiomyopathy), arthralgia, arthritis, and Raynaud's

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phenomenon. Patients may also have signs and symptoms of another connective tissue disease, such as systemic lupus erythematosus, scleroderma, or mixed connective tissue disease.

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Every sign and symptom listed for polymyositis can occur in patients with dermatomyositis, although myalgia and Raynaud's phenomenon are more common. The feature differentiating the two is the presence of cutaneous involvement. Skin changes can precede, coincide with, or develop after the onset of muscle weakness.

The most characteristic cutaneous manifestations of dermatomyositis include the heliotrope eruption (pink to violaceous erythema of the eyelids, occasionally with associated edema); Gottron's papules (raised erythematous to violaceous papules or plaques on the extensor surfaces of the metacarpophalangeal and interphalangeal joints); and Gottron's sign ANUPDAI=PKQOPKREKH=?AKQOI=?QHAOKJPDAAH>KSO GJAAO and lateral malleoli) (4). In addition to these classic clinical lJ@EJCO =@@EPEKJ=HOGEJI=JEBAOP=PEKJOEJ?HQ@AANUPDAI==J@ KNLKEGEHK@ANI=EJ=LDKPKOAJOEPERA@EOPNE>QPEKJ1ULE?=HOEPAO include the midface (which can mimic the malar rash of sysPAIE?HQLQOANUPDAI=PKOQO >QPEJRKHRAOPDAJ=OKH=>E=HBKH@O instead of sparing these sites), the anterior neck and chest

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