Common chronic disorder of the pilo-sebaceous unit, resulting in blockage of the follicle, formation of comedones and inflammation

Aetiology

• Age 12-24
• Family history
• Associated with some endocrine disorders: PCOS, hyperandrogenism

Pathophysiology

1. Increased androgens at puberty; patients may have increased androgen sensitivity of sebaceous glands
2. Hypercornification causes keratin plugging of pilosebaceous units
3. Infection with corynebacterium acnes (anaerobic bacterium)
4. Keratin and sebum build up to produce comedones (whiteheads/blackheads)
   1. Sebum production can be caused by increased androgens
5. Rupture causes acute inflammation and foreign body granulomas - produces the inflammatory lesions (papules, pustules, cysts and nodules)

Clinical features

• Distribution reflects sebaceous gland sites - face, upper back, anterior chest
• Non-inflammatory lesions (comodones): blackheads and whiteheads
• Inflammatory lesions: papules, pustules, cysts, nodules on erythematous base
• Scarring: atropic, hypertrophic, keloid
• Post- inflammatory hyper/hypopigmentation, post-inflammatory erythema
• Psychological dysfunction due to physical appearance

Classification of acne