Acne is an androgenically stimulated, inflammatory disorder of the sebaceous glands, resulting in comedones, papules, inflammatory pustules and, occasionally, scarring

• System(s) affected: Skin/Exocrine
• Genetics:
  • Approximately 50% of affected individuals have a family history of acne
  • Higher prevalence in Caucasians
• Incidence/Prevalence in USA: Virtually 100% of adolescents are affected to some degree. 15% will seek medical advice.
• Predominant age: Early to late puberty, although some cases will persist into the third and fourth decade. Age 16, 100% affected; 25-34, 8% affected; 35-44, 3% affected
• Predominant sex: Male = Female

• Closed comedones (whiteheads)
• Open comedones (blackheads)
• Nodules or papules
• Pustules, with or without redness and edema ("cysts")
• Scars - ice pick, atrophic macules, hypertrophic, depressed
• Lesions occur over the forehead, cheeks and nose, and may extend over the central chest and back
• Factors which influence symptomatology
  • Sex: males - later onset, greater severity; females: earlier onset, lesser severity
  • Seasonal variation - less severe in summer
  • May be worse immediately prior to menses
• Grading system
  • Grade 1: Comedonal - closed/open
  • Grade 2: Papular > 25 lesions on face & trunk
  • Grade 3: Pustular > 25 lesions, mild scarring
  • Grade 4: Nodulocystic - inflammatory nodules and cysts, extensive scarring

• Overproduction of androgens
• Hyperresponsiveness of follicle/sebaceous gland to androgens
• Hypersensitivity to P. acnes & its metabolic products
• Pathophysiology
  • Androgens stimulate sebum production & proliferation of keratinocytes in hair follicles
  • Keratin plug obstructs the follicle opening, resulting in sebum accumulation and follicular distention
  • Propionibacterium acnes, an anaerobe, colonizes & proliferates in the plugged follicle
  • P. acnes hydrolyzes sebum triglycerides into free fatty acids, produces chemotactic factors and proinflammatory mediators, and activates complement, all of which result in inflammation of the follicle and surrounding dermis

• Adolescence
• Male sex
• Androgenic steroids, e.g., steroid abuse, some birth control pills
• Oily cosmetics, including cleansing creams, moisturizers, oil-based foundations
• Rubbing or occluding the skin surface, as may occur with sports equipment (helmets and shoulder pads), holding the telephone or hands against the skin
• Drugs - iodides or bromides, lithium, phenytoin
• Systemic corticosteroids
• Virilization disorders
• Hot, humid climate