Inflammatory Myopathies in Children

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Juvenile idiopathic inflammatory myopathies are rare conditions that are probably autoimmune in nature. Juvenile dermatomyositis (JDM) is the most common inflammatory myopathy. This article describes a recent patient who presented with typical JDM and uses her case to discuss aspects of the childhood inflammatory myopathies.

Section snippets

The case

Kathryn is a 13-year-old white girl (Fig. 1) who met the diagnostic criteria of Bohan and Peter [1] at presentation. She initially was referred to the authors' by a dermatologist for typical Gottron's papules on her knuckles that developed within the 2 months before presentation. During 1 month she had developed progressive proximal muscle weakness associated with intermittent knee pain. On initial assessment, she had low-grade fever with malar rash and a heliotrope rash over the upper eyelids.

Epidemiology

Kathryn's presentation suggests several questions of an epidemiologic nature. How common is a case like this? Does ethnicity play a role in the frequency of JIIM? Is 13 years a typical age of presentation? Is it unusual to see JDM presenting in a girl?

It would seem from the literature that JIIM are quite rare. Several recent studies have demonstrated an incidence of about two to three cases per million children per year. For example, a survey study in Great Britain suggested that the incidence

Etiology and pathogenesis

Why did Kathryn develop JDM? She did not have a family history, nor did she have a personal history of a clear exposure to an infectious or environmental agent.

The etiology and pathogenesis of JIIM are unknown. Many potential pathogenic mechanisms have been suggested, including a genetic predisposition, the role of triggering factors such as infectious agents, and the role of complement and soluble adhesion molecules [7], [8]. Like other presumably autoimmune diseases, the JIIM probably result

Classification and diagnostic criteria

When Kathryn was referred to the Hospital for Sick Children, a diagnosis had not yet been made. It is appropriate to discuss how best to make a diagnosis of the JIIM and how best to classify these disorders.

Most centers still use the diagnostic criteria and classification system proposed in 1975 [1], [30]. There have been and continue to be attempts to update these criteria to take into account a broader understanding of the clinical and immunologic heterogeneity of the JIIMs and to incorporate

Diagnostic work-up

Kathryn had a number of tests at the time of diagnosis that allowed the authors to reach a diagnosis within the context of the Bohan and Peter criteria. What other tests should be done at diagnosis?

The initial assessment includes the recognition of a therapeutic emergency, such as respiratory distress or swallowing difficulties related to severe muscle weakness. Once these issues have been ruled out, the goal of the work-up is to confirm the first clinical impression and to classify the JIIM to

Clinical features

Kathryn presented with mild systemic symptoms and more marked musculoskeletal and dermatologic complaints. What other clinical signs and symptoms might have been seen?

Outcome measures

To follow patients in the clinic and to compare patients in clinical studies, it is helpful to use accurate and reliable outcome measurement tools. The Juvenile Dermatomyositis Disease Activity Collaborative Study Group, along with the International Myositis Assessment and Clinical Studies (IMACS) group, has worked to develop and validate new tools to assess disease activity and damage in JIIM. The tools most currently used are the Childhood Health Assessment Questionnaire (CHAQ), Manual Muscle

Therapy

Kathryn was treated with MTX and oral and, later, intravenous corticosteroids. What are the best therapies for children with JIIM? Is the oral or intravenous route of corticosteroids better? What other agents are available for these disorders?

Corticosteroids have been the traditional mainstay of therapy for the JIIM; onset is rapid, and clinical efficacy is seen within days to weeks. Toxicity with chronic use of corticosteroids is high, however. MTX seems to work well in JIIM, especially at

Clinical outcome

Kathryn is currently doing well, but what is her future prognosis? What will her school and work experience be? How long will she have her disease?

A few studies have reported the medium- and long-term functional outcomes of patients with JDM [40], [45], [50], [97], [98]. Bowyer and colleagues [50] have reported that delayed treatment leads to poorer outcome in terms of disease course and calcinosis. Huber and colleagues [98] looked at the outcomes of patients with JDM in an inception cohort

References (98)

  • A.V. Ramanan et al.

    Clinical features and outcomes of juvenile dermatomyositis and other childhood onset myositis syndromes

    Rheum Dis Clin North Am

    (2002)
  • T.M. Peloro et al.

    Juvenile dermatomyositis: a retrospective review of a 30-year experience

    J Am Acad Dermatol

    (2001)
  • B.M. Ansell

    Juvenile dermatomyositis

    Rheum Dis Clin North Am

    (1991)
  • R.E. Fisler et al.

    Aggressive management of juvenile dermatomyositis results in improved outcome and decreased incidence of calcinosis

    J Am Acad Dermatol

    (2002)
  • S.L. Bowyer et al.

    Childhood dermatomyositis: factors predicting functional outcome and development of dystrophic calcification

    J Pediatr

    (1983)
  • L.M. Pachman et al.

    Juvenile dermatomyositis: a clinical and immunologic study

    J Pediatr

    (1980)
  • J.D. Fortenberry et al.

    Fatal Pneumocystis carinii in an adolescent with systemic lupus erythematosus

    J Adolesc Health Care

    (1989)
  • A.D. Askari et al.

    Cardiac abnormalities in polymyositis/dermatomyositis

    Semin Arthritis Rheum

    (1982)
  • S. Bitnum et al.

    Dermatomyositis

    J Pediatr

    (1964)
  • H.M. Haupt et al.

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

    Am J Cardiol

    (1982)
  • R.A. El-Azhary et al.

    Amyopathic dermatomyositis: retrospective review of 37 cases

    J Am Acad Dermatol

    (2002)
  • B. Lang et al.

    Treatment of dermatomyositis with intravenous globulin

    Am J Med

    (1991)
  • J. Heckmatt et al.

    Cyclosporin in juvenile dermatomyositis

    Lancet

    (1989)
  • A. Paller et al.

    A 12-week study of tacrolimus ointment for the treatment of atopic dermatitis in pediatric patients

    J Am Acad Dermatol

    (2001)
  • A. Bohan et al.

    Polymyositis and dermatomyositis

    N Engl J Med

    (1975)
  • B.Q. Banker et al.

    Dermatomyositis (systemic angiopathy) of childhood

    Medicine (Baltimore)

    (1966)
  • D.P.M. Symmons et al.

    The incidence of juvenile dermatomyositis: results from a nation-wide study

    Br J Rheumatol

    (1995)
  • E.P. Mendez et al.

    US incidence of juvenile dermatomyositis, 1995–1998: results from the National Institute of Arthritis and Musculoskeletal and Skin Diseases Registry

    Arthritis Rheum

    (2003)
  • P. Ang et al.

    Classical and amyopathic dermatomyositis seen at the national centre of Singapore: a 3-year retrospective review of their clinical characteristics and association with malignancy

    Ann Acad Med Singapore

    (2000)
  • Cassidy JT, Petty RE, editors. Juvenile dermatomyositis. In: Textbook of pediatric rheumatology. 4th edition....
  • E.A. Shamim et al.

    Update on the genetics of the idiopathic inflammatory myopathies

    Curr Opin Rheumatol

    (2000)
  • C.M. Artlett et al.

    Persistent maternally derived peripheral microchimerism is associated with the juvenile idiopathic inflammatory myopathies

    Rheumatology (Oxford)

    (2001)
  • A.M. Reed et al.

    Does HLA-dependent chimerism underlie the pathogenesis of juvenile dermatomyositis

    J Immunol

    (2004)
  • C.M. Artlett et al.

    HLA-DQA1 is not an apparent risk factor for microchimerism in patients with various autoimmune diseases and in healthy individuals

    Arthritis Rheum

    (2003)
  • C.L. Verweij et al.

    Tumor necrosis factor alpha gene polymorphisms and rheumatic diseases

    Br J Rheumatol

    (1998)
  • A.G. Wilson et al.

    An allelic polymorphism within the human tumor necrosis factor alpha promoter region is strongly associated with HLA A1, B8, and DR3 alleles

    J Exp Med

    (1993)
  • A.G. Wilson et al.

    Effects of a polymorphism in the human tumor necrosis factor alpha promoter on transcriptional activation

    Proc Natl Acad Sci U S A

    (1997)
  • L.M. Pachman et al.

    TNFalpha-308A allele in juvenile dermatomyositis: association with increased production of tumor necrosis factor alpha, disease duration, and pathologic calcifications

    Arthritis Rheum

    (2000)
  • M. Massa et al.

    Self epitopes shared between human myosin and Streptococcus pyogenes M5 protein are targets of immune responses in active juvenile dermatomyositis

    Arthritis Rheum

    (2002)
  • Z. Tezak et al.

    Gene expression profiling in DQA1∗0501 + children with untreated dermatomyositis: a novel model of pathogenesis

    J Immunol

    (2002)
  • J.C. Wargula

    Update on juvenile dermatomyositis: new advances in understanding its etiopathogenesis

    Curr Opin Rheumatol

    (2003)
  • F.G.P. Goncalves et al.

    Immunohistological analysis of CD59 and membrane attack complex of complement in muscle in juvenile dermatomyositis

    J Rheumatol

    (2002)
  • A.M. Sallum et al.

    Immunohistochemical analysis of adhesion molecule expression on muscle biopsy specimens from patients with juvenile dermatomyositis

    J Rheumatol

    (2004)
  • C.K.C. Li et al.

    MHC class I overexpression on muscles in early juvenile dermatomyositis

    J Rheumatol

    (2004)
  • A. Bohan et al.

    Polymyositis and dermatomyositis

    N Engl J Med

    (1975)
  • B.M. Feldman et al.

    Clinical significance of specific autoantibodies in juvenile dermatomyositis

    J Rheumatol

    (1996)
  • A.B. Kimball et al.

    Magnetic resonance imaging detection of occult skin and subcutaneous abnormalities in juvenile dermatomyositis

    Arthritis Rheum

    (2000)
  • S.M. Maillard et al.

    Quantitative assessment of MRI T2 relaxation time of thigh muscles in juvenile dermatomyositis

    Rheumatology

    (2004)
  • L.M. Pachman et al.

    Juvenile dermatomyositis at diagnosis: clinical characteristics of 79 children

    J Rheumatol

    (1998)

    • A version of this article originally appeared in the 52:2 issue of Pediatric Clinics of North America.

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