What is lichen planus?
Lichen planus is a fairly common, itchy, non-infectious type of rash that usually occurs in adults. Doctors use the word ‘lichen’ to mean small bumps on the skin. ‘Planus’ means ‘flat’, and tells us that the small itchy bumps that make up the rash of lichen planus have shiny flat tops.
What causes lichen planus?
The cause of lichen planus is still not known, but is likely to have something to do with the body’s defences – the immune system. Rashes that look like lichen planus – known as ‘lichenoid drug eruptions’ – are sometimes a reaction to taking medicines such as gold (used for arthritis) or antimalarial tablets. Lichen planus is not contagious.
Is lichen planus hereditary?
Usually it is not but, rarely, a few members of the same family can have it.
What are the symptoms of lichen planus?
Lichen planus on the skin is usually itchy.
What does lichen planus look like?
The rash is made up of shiny, 3-5mm, slightly raised purple-red spots. A close look is needed to see the irregular white streaks that lie on the flat surface of some of them. The spots arise most often on the fronts of the wrists, around the ankles and on the lower back, but can spread more widely. In addition, lichen planus sometimes comes up in lines where the skin has been scratched or cut.
Other types of lichen planus include a thickened ('hypertrophic') lichen planus, which tends to affect the shins, and a ring-shaped ('annular') lichen planus, which usually comes up in the creases such as the armpits. Lichen planus occasionally appears on the scalp where it can cause hair loss, or may damage the nails (thinning and grooving of the nail plate), though this is rare.
Lichen planus is common in the mouth and is present in about 30-70% of those who have it on their skin (see patient information leaflet for Oral Lichen Planus).
Lichen planus can affect the penis in men, causing purple-coloured or white ring-shaped patches. Unlike other patches of lichen planus, these often do not itch. Lichen planus can affect the genital area in women too, but this is less common.
Most patients with lichen planus clear up within 18 months and usually stay clear, although some have a second episode many years later. Unfortunately some types of lichen planus, such as oral, hair or nail involvement, can last for many years. Even after the active lichen planus has cleared up, pigmented stains in the skin may persist for a long time, particularly in Asian or Afro-Caribbean skin.
How will lichen planus be diagnosed?
Usually the diagnosis of lichen planus can be made easily enough just by the look of the rash. Confusion may arise with flat ‘plane’ warts, with some types of eczema, and with rashes due to some drugs. If there is real doubt, the diagnosis can be clinched by looking under the microscope at a small sample of skin (a biopsy specimen) removed after a local anaesthetic injection.
Can lichen planus be cured?
No, treatment damps it down but does not switch it off. However, lichen planus usually goes away by itself.
For information about available treatments please visit this page on the website of the British Association of Dermatologists
Thanks to the American Academy of Dermatology for the above image.