Elsevier

The Lancet

Volume 362, Issue 9388, 20 September 2003, Pages 971-982
The Lancet

Seminar
Polymyositis and dermatomyositis

https://doi.org/10.1016/S0140-6736(03)14368-1Get rights and content

Summary

The inflammatory myopathies, commonly described as idiopathic, are the largest group of acquired and potentially treatable myopathies. On the basis of unique clinical, histopathological, immunological, and demographic features, they can be differentiated into three major and distinct subsets: dermatomyositis, polymyositis, and inclusion-body myositis. Use of new diagnostic criteria is essential to discriminate between them and to exclude other disorders. Dermatomyositis is a microangiopathy affecting skin and muscle; activation and deposition of complement causes lysis of endomysial capillaries and muscle ischaemia. In polymyositis and inclusion-body myositis, clonally expanded CD8positive cytotoxic T cells invade muscle fibres that express MHC class I antigens, which leads to fibre necrosis via the perforin pathway. In inclusion-body myositis, vacuolar formation with amyloid deposits coexists with the immunological features. The causative autoantigen has not yet been identified. Upregulated vascular-cell adhesion molecule, intercellular adhesion molecule, chemokines, and their receptors promote T-cell transgression, and various cytokines increase the immunopathological process. Early initiation of therapy is essential, since both polymyositis and dermatomyositis respond to immunotherapeutic agents. New immunomodulatory agents currently being tested in controlled trials may prove promising for difficult cases.

Section snippets

Epidemiology, genetics, and general clinical features

Dermatomyositis affects both children and adults, and women more than men. Polymyositis is seen after the second decade of life. Inclusion-body myositis is more common in men over the age of 50 than in other population groups.1, 2, 3, 4, 5, 6, 7 The frequencies of polymyositis and dermatomyositis as stand-alone disorders or in association with other systemic diseases are unknown. Estimates based on old diagnostic criteria,8 which cannot distinguish polymyositis from inclusion-body myositis,1, 3

Dermatomyositis

Dermatomyositis is identified by a characteristic rash accompanying or, more commonly, preceding muscle weakness. The skin manifestations include a heliotrope rash (blue-purple discolouration) on the upper eyelids in many cases associated with oedema, and an erythematous rash on the face, neck, and anterior chest (in many patients in a V sign) or back and shoulders (shawl sign), knees, elbows, and malleoli; the rash can be exacerbated after exposure to the sun and is pruritic in some cases.

Extramuscular manifestations

There are many manifestations outside the muscles. Joint contractures occur mostly in dermatomyositis. Dysphagia is due to involvement of the oropharyngeal striated muscles and upper oesophagus30, 31 (gastrointestinal ulcerations due to vasculitis and infection were common in children with dermatomyositis before the use of immunosuppressants2). Cardiac disturbances include atrioventricular conduction defects, tachyarrhythmias, myocarditis in patients with acute disease,32, 33 and heart failure

Diagnosis

The clinical diagnosis of polymyositis and dermatomyositis is confirmed by three laboratory examinations: serum muscle enzyme concentrations, electromyography, and muscle biopsy. In certain cases of dermatomyositis, skin biopsy can be helpful.

The most sensitive muscle enzyme assay is creatine kinase, which is increased up to 50 times in active disease. Aspartate and alanine aminotransferases, lactate dehydrogenase, and aldolase are also increased. Although creatine kinase concentration usually

Diagnostic criteria

The subject of diagnostic criteria remains unsettled because the various proposed criteria3 have not been properly validated. The criteria of Bohan and Peter8 cannot distinguish polymyositis from inclusion-body myositis or from certain dystrophies. Because the immunopathological characteristics confer specificity for each subset, we believe that the diagnostic criteria should rely on histopathology and immunopathology as the best means of separating polymyositis from other myopathies.1

Immunopathogenesis

The autoimmune origin of polymyositis and dermatomyositis is supported by their association with other autoimmune disorders, autoantibodies,60 and histocompatibility genes; the evidence of T-cell-mediated myocytotoxicity or complement-mediated microangiopathy; the possible maternal microchimerism in juvenile forms;61 and their response to immunotherapies. However, no specific target antigens have been identified, and the agents initiating self-sensitisation remain unknown.

Treatment

The goals of therapy are to improve the ability to carry out activities of daily living by increasing muscle strength and to ameliorate extramuscular manifestations (rash, dysphagia, dyspnoea, arthralgia, fever). There have been very few controlled clinical trials, most on dermatomyositis and inclusion-body myositis.135 Overall, dermatomyositis responds better than polymyositis, and inclusion-body myositis is difficult to treat. Although when the strength improves, the serum creatine kinase

Prognosis

Although the disease outcome has substantially improved, at least a third of patients are left with mild to severe disability.154, 155, 156 Older age and association with cancer are factors associated with poor prognosis. Pulmonary fibrosis, frequent aspiration pneumonias due to oesophageal dysfunction, and calcinosis in dermatomyositis are associated with increased morbidity.154, 155, 156 In a small cohort, the 5-year survival was 95% and the 10-year survival 84%.156

Conclusion

On the basis of our own experience and that of others in major neuromuscular centres, the diagnosis and treatment of dermatomyositis and polymyositis could be improved by modification of many common practices. First, all disorders that mimic polymyositis should be excluded, taking into account that the criteria of Bohan and Peter cannot separate polymyositis from inclusion-body myositis or other toxic, necrotising, and dystrophic myopathies. Second, polymyositis as a stand-alone entity is rare.

Search strategy and selection criteria

The review is based on our own experience and research connected with these disorders as well as a comprehensive MEDLINE search on the topics of “polymyositis”, “dermatomyositis”, and “inflammatory myopathies”. We focused on peer-reviewed works published in English in major scientific journals over the past 10 years and on reviews written by experts on this subject. All available articles were critically reviewed. Papers presenting the strongest evidence or providing important insights

References (156)

  • HauptHM et al.

    The heart and cardiac conduction system in polymyositis-dermatomyositis: a clinicopathologic study of 16 autopsied patients

    Am J Cardiol

    (1982)
  • HillCL et al.

    Frequency of specific cancer types in dermatomyositis and polymyositis: a population-based study

    Lancet

    (2001)
  • DalakasMC

    Muscle biopsy findings in inflammatory myopathies

    Rheum Dis Clin N Am

    (2002)
  • HohlfeldR et al.

    The immunobiology of muscle

    Immunol Today

    (1994)
  • Emslie-SmithAM et al.

    Major histocompatibility complex class I antigen expression, immunolocalization of interferon subtypes and T-cell- mediated cytotoxicity in myopathies

    Hum Pathol

    (1989)
  • TargoffIN

    Laboratory testing in the diagnosis and management of idiopathic inflammatory myopathies

    Rheum Dis Clin N Am

    (2002)
  • ReedAM et al.

    Chimerism in children with juvenile dermatomyositis

    Lancet

    (2000)
  • FriedmanAW et al.

    Interstitial lung disease with autoantibodies against aminoacyl-tRNA synthetases in the absence of clinically apparent myositis

    Semin Arthritis Rheum

    (1996)
  • LundbergI et al.

    Analysis of cytokine expression in muscle in inflammatory myopathies, Duchennes dystrophy and non-weak controls

    J Neuroimmunol

    (1995)
  • LiM et al.

    Expression of human IAP-like protein in skeletal muscle: an explanation for the rare incidence of muscle fiber apoptosis in T-cell mediated inflammatory myopathies

    J Neuroimmunol

    (2000)
  • DalakasMC

    The molecular and cellular pathology of inflammatory muscle diseases

    Curr Opin Pharmacol

    (2001)
  • EnglundP et al.

    Skeletal muscle fibers express major histocompativility complex class II antigens independently of inflammatory infiltrates in inflammatory myopathies

    Am J Pathol

    (2001)
  • DalakasMC

    Polymyositis, dermatomyositis and inclusion-body myositis

    N Engl J Med

    (1991)
  • EngelAG et al.

    The polymyositis and dermatomyositis syndromes

  • DalakasMC et al.

    The inflammatory myopathies

  • Hilton-JonesD

    Inflammatory myopathies

    Curr Opin Neurol

    (2001)
  • DalakasMC

    Polymyositis, dermatomyositis and inclusion body myositis

  • SekulEA et al.

    Inclusion body myositis: new concepts

    SeminNeurol

    (1993)
  • BohanA et al.

    Polymyositis and dermatomyositis

    N Engl J Med

    (1975)
  • PlotzPH et al.

    Current concepts in the idiopathic inflammatory myopathies: polymyositis, dermatomyositis and related disorders

    Ann Intern Med

    (1989)
  • MedsgerTA et al.

    The epidemiology of polymyositis

    Am J Med

    (1979)
  • ShaminEA et al.

    Update on the genetics of the idiopathic inflammatory myopathies

    Curr Opin Rheumatol

    (2000)
  • ShaminEA et al.

    Differences in idiopathic inflammatory myopathy phenotypes and genotypes between Mesoamerican Mestizos and North American Caucasians

    Arthritis Rheum

    (2002)
  • ReedAM

    Myositis in children

    Curr Opin Rheumatol

    (2001)
  • OteroC et al.

    Is there dermatomyositis (DM) without myositis?

    Neurology

    (1992)
  • MimoriT

    Scleroderma-polymyositis overlap syndrome: clinical and serologic aspects

    Int J Dermatol

    (1987)
  • HertzmanPA et al.

    Association of the eosinophilia-myalgia syndrome with the ingestion of tryptophan

    N Engl J Med

    (1990)
  • DoyleDR et al.

    Fatal polymyositis in D-penicillamine-treated rheumatoid arthritis

    Ann Intern Med

    (1983)
  • DalakasMC et al.

    Mitochondrial myopathy caused by long-term zidovudine therapy

    N Engl J Med

    (1990)
  • MastagliaFL

    Adverse effects of drugs on muscle

    Drugs

    (1982)
  • DalakasMC

    Diseases of muscle and the neuromuscular junction

    SciAm

    (1997)
  • DietzF et al.

    Cricopharyngeal muscle dysfunction in the differential diagnosis of dysphagia in polymyositis

    Arthritis Rheum

    (1980)
  • DeMerieuxP et al.

    Esophageal abnormalities and dysphagia in polymyositis and dermatomyositis: clinical, radiographic and pathologic features

    Arthritis Rheum

    (1983)
  • QuartierP et al.

    Severe cardiac involvement in children with systemic sclerosis and myositis

    J Rheumatol

    (2002)
  • LakhanpalS et al.

    Pulmonary disease in polymyositis/dermatomyositis: a clinicopathological analysis of 65 autopsy cases

    Ann Rheum Dis

    (1987)
  • HirakataM et al.

    Interstitial lung disease in polymyositis and dermatomyositis

    Curr Opin Rheumatol

    (2000)
  • DouglasWW et al.

    Polymyositis-dermatomyositis associated interstitial lung disease

    Am J Respir Crit Care Med

    (2001)
  • DalakasMC

    Calcifications in dermatomyositis

    N Engl J Med

    (1995)
  • SigurgeirssonB et al.

    Risk of cancer in patients with dermatomyositis or polymyositis: a population-based study

    N Engl J Med

    (1992)
  • BuchbinderR et al.

    Incidence of malignant disease in biopsy-proven inflammatory myopathy

    Ann Intern Med

    (2001)
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