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.


Classification by Severity

  • Usually overestimated by patient and underestimated by physician
Mild Moderate Severe
Comedones <20 20-100 >100
Papules/Pustules <15 15-50 >50
Nodules/Cysts 0 <5 >5
Total Lesion Count <30 30-125 >125

Severe Papules/Pustules or Nodulocystic Acne

  • Acne that is resistant to topical treatment or if scarring/nodular lesions are present

Other Considerations

  • Grading schemes that rely on the above lesion counts are usually of greater use in clinical studies rather than clinical practice
  • May be better to focus on the most severe lesions present
    • Proper treatment of the most severe lesions usually covers all lesser lesions


  • History of past treatments
  • In most cases, there is no need to look for underlying cause, which may be found in patients >20 year & in resistant acne cases

Physical Examination

  • Diagnosis is usually confirmed based on the morphology of the lesions and their site of distribution

Types of Acne Lesions

  • Comedonal (non-inflammatory)
    • Closed (whitehead) or open (blackhead)
  • Papulopustular (inflammatory)
    • Papule: Small bump <5 mm in diameter
    • Pustule: Smaller bump with core of purulent material
  • Nodular (inflammatory)
    • Nodule >5 mm

Site of Distribution

  • Lesions typically concentrate in the centrofacial areas
    • Forehead, nose, chin
  • May eventually involve other areas containing sebaceous glands
    • Face, ears, neck, chest, shoulders, back, scalp
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