Pityriasis Lichenoides
What are the aims of this leaflet?
This leaflet has been written to help you understand more about pityriasis lichenoides. It tells you what it is, what causes it, what can be done about it, and where you can find out more about it.
What is pityriasis lichenoides?
Pityriasis lichenoides is a rare skin disorder that is limited to the skin. The term ‘pityriasis lichenoides’ means that the rash is scaly (pityriasis) and that it was once thought to look like a lichen (a type of plant that lives on rocks) because it is made up of small bumpy areas.
There are two types of pityriasis lichenoides: an acute form usually found in children (known as pityriasis lichenoides et varioliformis acuta (PLEVA)), and a more long-lasting form known as pityriasis lichenoides chronica (PLC).
What causes pityriasis lichenoides?
The cause of pityriasis lichenoides is not known, but the symptoms that occur in the childhood form suggest that it may be an inflammatory reaction to a viral or bacterial infection. It has also been considered a benign skin proliferation of immunological cells (T cells). It is more common in males than females. Neither type of pityriasis lichenoides is infectious.
Is it hereditary?
No.
What are the symptoms of pityriasis lichenoides?
The main thing you will notice is raised spots that tend to come in crops. New spots can itch or irritate as they come up.
What does pityriasis lichenoides look like?
- The acute form (PLEVA):There may be a mild illness with a fever. The rash starts as separate pink spots, which form a little blister and may turn black. A crust forms on the surface and drops off to leave a small scar. The spots come up in crops, and so the rash consists of spots at various stages of development; some are small pink bumps, others have small blisters on top, and others are black in colour. The rash can look like chickenpox but takes much longer to clear. It rarely affects the face, but the spots are usually scattered on the trunk and limbs.
- The chronic form (PLC): The spots look less angry and are covered with a firm shiny scale. A good diagnostic pointer is the way this scale, covering the top of a spot, can be scraped off as a single chunk, to reveal a shiny brownish surface underneath. The spots fade within 3 to 4 weeks, but new spots may then arise. The rash can clear up within a few weeks or persist for years.
How will it be diagnosed?
The look of the rash suggests the diagnosis; however, PLEVA can look like chickenpox (though it lasts much longer) and PLC can look like psoriasis, lichen planus or even insect bites. The examination of a small sample of the rash (a skin biopsy) under the microscope should confirm the diagnosis.
Can it be cured?
No treatment is certain to cure pityriasis lichenoides.
How can it be treated?
Reports suggest that antibiotics given for one month may help some patients. Natural sunlight may be effective, and treatment with special ultraviolet light lamps (not ordinary sun beds) can also help. Lamps that produce UVB or UVA (different wavelengths of ultraviolet light) are both useful, as is the combination of tablets known as Psoralens with UVA(PUVA treatment). PUVA has a greater effect on improving the skin, but carries a higher risk of side effects. There have been some reports that suggest that methotrexate tablets might help the more severe forms of the disease.
What can I do?
If the rash is not a nuisance, you may not need treatment.
Where can I find out more about pityriasis lichenoides?
Links to other Internet sites:
www.thedoctorsdoctor.com/diseases/pleva.htm
www.dermnetnz.org/dna.pitlic/pitlic.html