Acne vulgaris is a chronic inflammatory dermatosis which is notable for open and/or closed comedones (blackheads and whiteheads) and inflammatory lesions including papules, pustules or nodules.
Mild acne has <20 comedones or <15 inflammatory lesions or <30 total lesion count.
Moderate acne has 20-100 comedones or 15-20 inflammatory lesions or 30-125 total lesion count.
Severe papules/pustules or nodulocystic acne is the acne resistant to topical treatment or if scarring/nodular lesions are present.


  • Acne vulgaris is a chronic inflammatory dermatosis which is notable for open and/or closed comedones (blackheads & whiteheads) and inflammatory lesions including papules, pustules, or nodules

Risk Factors

Contributing Factors

  • Medications
    • Corticosteroids, anabolic steroids, Lithium, some OC, etc
  • Androgen excess
    • Signs of androgen excess: Precocious puberty, hirsutism, irregular menstruation, androgenetic alopecia
    • Causes of androgen excess: Polycystic ovary disease or adrenal, ovarian, or pituitary tumor
    • Pathogenesis: Androgen excess causes abnormal epithelial desquamation and obstruction of follicles, the latter secondary to sebum production forming open and closed comedones. Propionibacterium acne proliferates due to sebum and causes inflammation manifested as papules, pustules, nodules, and cysts
  • Mechanical
    • Physical occlusion: Eg cosmetics, hats, head bands, etc
  • Other factors for which evidence is limited
    • Consumption of westernized diet, intake of skim milk, stress
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