An itchy rash consisting of small, raised, flat-topped lesions that are shiny and pink or purple in colour
In lichen planus, small, shiny, flattened, pink or purple, itchy lesions appear in a dense cluster. Often, there is no obvious cause, but occasionally the rash may develop as a reaction to certain drugs, such as sulphonamide antibiotics or gold-based antirheumatic drugs. Lichen planus may be associated with stress. It is more common in people over the age of 30.
The rash can develop in patches on the lower back and on the inner surfaces of the wrists, forearms, and ankles. Lichen planus often appears suddenly and may affect more than one area, but sometimes the rash spreads gradually over a period of a few months. The symptoms of lichen planus include:
Groups of small, shiny, pink or purple, flat-topped lesions on the skin; the surface of some may be covered by a network of fine white lines.
Intense itching, particularly at night.
The disorder can also affect the nails and scalp. If lichen planus develops in the nails, they become ridged along their length and, in some cases, fall off (see Nail abnormalities).
If the scalp is affected, patchy hair loss with associated scarring of the scalp may occur. The lesions may also appear on the sites of skin injury such as scratches. Another form of lichen planus affects the mouth (see Oral lichen planus).
If the diagnosis is not obvious from the appearance of the rash, your doctor may arrange for a skin biopsy, in which a sample of skin is removed and examined under a microscope. To relieve the itching, the doctor may prescribe a strong topical corticosteroid. In addition, you can take an over-the-counter oral antihistamine (see Antipruritic drugs) for relief at night. If the rash is widespread and affects your nails or scalp, you may need oral corticosteroid drugs.
If a drug reaction is suspected, your doctor will advise you to stop taking the drug and may prescribe an alternative. Lichen planus usually persists for 12–18 months but may sometimes last for many years. It may leave patches of darkened skin where it has healed.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.