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Interface Dermatitis

Pityriasis Lichenoides

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Clinical Features

  
      Self-limited cutaneous eruption of unknown cause that affects young adults and children
      Two forms are recognized
      Mucha-Habermann disease
      An acute, more severe form also known as pityriasis lichenoides et varioliformis acuta

      Pityriasis lichenoides chronica
      Chronic, milder form

      Occasional transitional forms with changes between the two extremes occur

      In pityriasis lichenoides et varioliformis acuta, a papular, papulonecrotic, and occasionally vesiculopustular eruption occurs on trunk and proximal extremities and usually resolves in a few weeks; crops of new lesions can continue to appear, and the disease process itself may have a chronic course
      In pityriasis lichenoides chronica, recurrent crops of reddish-brown papules with adherent scales occur on trunk and extremities and resolve in a few weeks

Histopathology

  
      Parakeratosis and a scale crust with neutrophils in severe cases
      Epidermal …