Definition and description
Lichen Planus (LP) is a disorder of unknown cause, affecting the skin and mucous membranes.
It appears as single or clustered papules (bumps), which are itchy, flat-topped and purplish in colour. Common sites are the wrist and ankle, but they may appear inside the mouth or even the vagina, and may in rare cases affect the oesophagus. LP typically affects middle-aged adults, with recurrences lasting weeks or months. It is not infectious or contagious.
Causes and associated conditions
There is no definite known cause, but it may be a form of auto-immune disease, with auto-antibodies against basal skin cells.
There is an association with liver disease, notably in advanced disease due to Hepatitis C.
A drug-induced form is also known, linked to the use of:
- Non-steroidal anti-inflammatories
- Beta blockers, quinidine, diuretics & ACE inhibitors used for heart problems
- Quinidine, gold, phenothiazines, and some anti-diabetic agents
Long-standing mouth LP has a risk of developing malignant change.
The commonest presentation is of a single lesion, or a cluster of lesions, usually on the inner wrist. The papules are nearly always itchy, purplish, shiny, and may have white streaks. Once healed, they may leave areas of increased pigmentation.
In the mouth, they may appear more greyish, and are mostly found on the sides of the tongue and inner cheek. Mouth LP is often painful, and the papules may blister and ulcerate.
On the scalp, LP lesions can cause areas of hair loss, which may be permanent if the hair follicle is damaged or destroyed, especially if treatment is delayed.
LP can also affect the nails, causing anything from minor abnormalities to complete loss of the nail. This form is often resistant to treatment.
The diagnosis of LP is clinical, but a biopsy may be needed to exclude some conditions which appear very similar, such as
- Oral leukoplakia
- Lichenoid drug reaction
- Discoid lupus erythematosus
- Chronic ulcerative stomatitis
If hepatitis or drug induced LP is suspected, appropriate blood tests may be done.
There is no known cure for LP, but symptom relief may be obtained by using several medications:
- Anaesthetic preparations; for example mouthwash, creams for vulvo-vaginal LP
- Corticosteroids: injected into the papules (also for scalp involvement); orally for widespread or oesophageal LP (concomitant used of an anti-fungal is recommended to avoid oesophageal candidiasis); topically
- Retinoic acid cream, often used with cortisone creams
- Ultra-violet light exposure - controversial
- Tacrolimus - for cortisone resistant cases
- Hydrochloroquin and dapsone may also be tried.
LP is an incurable, chronic, recurrent condition. Each episode may last for months at a time, and healing often leaves hyper-pigmented skin patches. Patients may develop psycho-social problems due to this chronic disorder, which is often very visible.
Dr. AG Hall