Psoriasis is a chronic, inflammatory skin disease. Knees, elbows, scalp, trunk, and nails are the most commonly affected areas. There are several types of psoriasis:

  • Plaque—inflamed patches of skin topped with silvery, white scales (most common type)
  • Guttate—small dot-like lesions
  • Pustular—weeping lesions and intense scaling
  • Inverse (intertriginous)—inflamed patches of skin in body folds (armpits, groin, under breasts)
  • Erythrodermic—intense sloughing and inflammation of nearly the entire skin

Psoriasis
Psoriasis
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The cause of psoriasis is unclear. Signals from a defect in the immune system may result in an overgrowth of skin cells. Because the cells grow faster than they can be shed, they pile up on the skin's surface. The excess skin cells are thought to cause the silvery white scales that are characteristic of plaque-type psoriasis.