Acne vulgaris is a common skin disorder which usually occurs in adolescence. It typically affects the face, neck and upper trunk and is characterised by the obstruction of the pilosebaceous follicles with keratin plugs which results in comedones, inflammation and pustules.

Epidemiology: 20-35% of adolescents are affected by moderate or severe acne vulgaris  in western countries.

Pathophysiology

pilosebaceous units - contain the hair follicles and sebaceous glands. The sebaceous glands produce the natural skin oils and a waxy substance known as sebum.

Acne results from increased production of sebum, trapping of keratin (dead skin cells) and blockage of the pilosebaceous unit. This leads to swelling and inflammation in the pilosebaceous unit.

The Propionibacterium acnes bacteria is felt to play an important role in acne. This is a bacteria that colonises the skin. It is thought that excessive growth of this bacteria can exacerbate acne. Many of the treatments of acne aim to reduce these bacteria.

Acne may be classified into mild, moderate or severe:

• mild: open and closed comedones with or without sparse inflammatory lesions
• moderate acne: widespread non-inflammatory lesions and numerous papules and pustules
• severe acne: extensive inflammatory lesions, which may include nodules, pitting, and scarring

Risk factors:

• Age 12-24
• Genetic predisposition
• Greasy skin/increased sebum production (in puberty, androgens stimulate sebaceous glands to produce more sebum)
• Medications - Androgens, steroids, antiepileptics, lithium, ACTH
  • Increase sebum production
• Endocrine disorders - PCOS