Skin nontumor

Folliculitis, perifolliculitis and disease of skin appendages

Acne vulgaris

Last author update: 1 July 2011
Last staff update: 6 August 2020

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PubMed Search: Acne vulgaris [title] skin

Mowafak Hamodat, M.B.Ch.B., M.Sc.
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Cite this page: Hamodat M. Acne vulgaris. website. Accessed September 21st, 2023.
Definition / general
  • Common skin disease of seborrhea (scaly red skin), comedones (blackheads and whiteheads), papules (pinheads), pustules (pimples), nodules (large papules) and possibly scarring
  • Typically affects skin with densest sebaceous follicles: face, upper chest, back; uncommon in scalp for unknown reasons
  • Acne vulgaris is common acne, typically with comedones
  • Acne rosacea is a different disorder
  • Due to hormonal variations and alterations in hair follicle maturation
  • Begins with abnormal follicular keratinization with retention of keratinous material in the follicle
  • Then increased sebum production
  • Then appearance of gram positive, anaerobic, diphtheroid Propionibacterium acnes
  • May become inflammatory
Diagrams / tables

Images hosted on other servers:

Stages of acne

Clinical features
  • Usually teenagers of either sex, but often more severe in males
  • Worsens with drugs (steroids, testosterone, contraceptives), oils / tars, heavy clothing and tropical climates
  • Non-inflammatory acne is due to open and closed comedones
  • Open comedones: small follicular papules with central, black keratin plug (due to oxidation of melanin)
  • Closed comedones: follicular papules with a deeper plug below the surface
  • Follicles may rupture and become inflamed
  • Diverse lesions such as comedones, papules, pustules, cysts, sinuses and scars
Clinical images

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Various images

Microscopic (histologic) description
  • 3 major components are comedones, inflammatory lesions and scars
  • Comedones (open or closed) are cyst-like cavities filled with compact mass of keratinous material and numerous bacteria
  • Closed comedo has 1 - 2 hairs trapped in lumen and atrophic, sebaceous acini
  • Open comedo has 10 - 15 hairs in lumen and sebaceous acini are atrophic or absent
  • Epithelial lining of comedones is usually thin
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