Pityriasis lichenoides

Pityriasis lichenoides has an acute and chronic phase

• acute form is called Pityriasis lichenoides et varioliformis acuta (PLEVA) or Mucha-Habermann disease
  • characterised by red patches that quickly evolve into papules 5-15 mm in diameter
  • often covered with a fine mica-like adherent scale
  • centre of the papules often becomes filled with pus and blood, or eroded with overlying red-brown crust
  • most often occurs on the trunk and extremities but sometimes may also be diffuse and widespread, covering any part of the body
  • patients with PLEVA experience burning and itchiness
    
    
• chronic form is usually designated as pityriasis licehnoides chronica (PLC)
  • more low-grade clinical course than PLEVA
  • lesions may appear over the course of several days, weeks or months.
    • lesions at various stages may be present at any one time
    • the initial lesion is a small pink papule occurs that turns a reddish-brown colour
      • generally a fine mica-like adherent scale attached to the central spot develops. This can be peeled off to reveal a shiny, pinkish brown surface
      • the spot flattens out spontaneously over several weeks and leaves behind a brown mark, which fades over several months
      • most commonly occurs over the trunk, buttocks, arms and legs, but may also occur on the hands, feet, face and scalp.
      • lesions are not painful, itchy or irritable
      • may be exacerbations and relapses of the condition, which can last for months or years
        
        
• two diseases from a spectrum of a self-limited dermatosis with the acute form starting as a maculopapular, erythematous eruption which heals to form superficial variable scars
  
  
• lesions occur in crops over several weeks and may continue for months to years
  
  
• chronic form is more scaly and less hemorrhagic
  
  
• is a predilection for males in the second and third decades
  
  
• pityriasis lichenoides is not an uncommon disease in childhood, with age peaks in the preschool and early school-age years. It is usually recurrent, and shows a seasonal variation with onset most often in the fall or winter. In childhood PL, erythromycin is an effective initial treatment choice (1)
  
  
• most common on the anterior trunk and flexor surfaces of the proximal portions of the extremities

Management:

• seek expert advice
• pityriasis lichenoides may not always be responsive to treatment
  • relapses often occur when treatment is discontinued
• if the rash is asymptomatic
  • treatment may not be necessary
• first-line therapies include:
  • sun exposure may help to resolve lesions
    • sunburn should be avoided
  • topical steroids to reduce irritation.
  • topical immunomodulators such as tacrolimus or pimecrolimus
  • oral antibiotics
    • most common antibiotics used are erythromycin and tetracyclines such as doxycycline
• second-line therapies include:
  • phototherapy - artificial ultraviolet radiation treatment with UVB or PUVA has been used with varying success both in patients with PLEVA and in those with PLC
    
    

Images of pityriasis lichenoides

Reference:

• Ersoy-Evans S et al. Pityriasis lichenoides in childhood: a retrospective review of 124 patients.J Am Acad Dermatol. 2007 Feb;56(2):205-10.
• Bowers S, Warshaw EM. Pityriasis lichenoides and its subtypes. J Am Acad Dermatol 2006;55:557-72