Skin-nontumor / Clinical dermatology
Other dermatoses
Dermatomyositis

Author: Mowafak Hamodat, M.D., MB.CH.B, MSc., FRCPC (see Authors page)

Revised: 24 June 2016, last major update July 2011

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PubMed Search: Dermatomyositis [title] skin

Definition / General
  • See also Muscle chapter
  • Autoimmune inflammatory disease of skeletal muscle and skin, usually affects women
  • Symmetric proximal muscle weakness and skin lesions
  • Affects face, dorsal hands and feet, particularly knuckles
  • 20% of cases lack muscle involvement (Arch Dermatol 2010;146:26)
  • 15% have coexisting adenocarcinoma of stomach, breast, ovary, lung or colon, with remission of dermatomyositis following tumor resection; high risk of nasopharyngeal carcinoma in Asian patients (Ann Acad Med Singapore 2010;39:843)
  • Increased risk of thyroid disease, particularly hypothyroidism, especially in patients with interstitial lung disease

  • Polymyositis: similar muscle changes without skin changes
Clinical Features
  • Poorly demarcated, scaly, erythematous patches
  • Also heliotrope erythema of upper eyelids and extensor joint surfaces
Treatment
Clinical Images

Images hosted on other servers:

Purple plaques on knees

Heliotrope rash and Gottron's papules

Various images

Micro Description
  • Chronic nonspecific dermatitis or interface dermatitis resembling systemic lupus erythematosus
  • Often atrophic epidermis with prominent vacuolar interface change
  • Sparse perivascular lymphocytic infiltrate with markedly increased dermal mucin
  • Muscles show myositis with myofiber necrosis, fragmentation and phagocytosis; late myofiber atrophy, fibrosis and fatty change
Micro Images

Images hosted on other servers:

Erythrodermic dermatomyositis

Interface dermatitis with vacuolar alteration at dermal-epidermal junction

Positive Stains
  • C5-9 (by immunofluorescence)
Negative Stains
  • IgG, IgA, and IgM by immunofluorescence
Additional References