Skin inflammatory (nontumor)
Lichenoid and interface reaction patterns

Author: Mowafak Hamodat, M.D., MB.CH.B, MSc.

Revised: 15 October 2018, last major update July 2011

Copyright: (c) 2002-2018,, Inc.

PubMed Search: Dermatomyositis [title] skin "loattrfree full text"[sb]

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Cite this page: Hamodat, M. Dermatomyositis. website. Accessed March 22nd, 2019.
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
Clinical images

Images hosted on other servers:

Purple plaques on knees

Heliotrope rash and Gottron's papules

Various images

Microscopic (histologic) 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
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Hillary Rose Elwood, M.D.

Subtle vacuolar interface change and increased dermal mucin highlighted by Alcian blue stain

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
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