How do I know if my patient has lichen planus?

A case-based review with clinical images of the diagnosis and management of lichen planus.
How do I know if my patient has lichen planus?

A 60-year-old patient presents to your surgery with his daughter. He has Parkinson's disease (PD) and tends to be prone to dribbling. When you are examining him you notice that he has a rather white tongue mainly on the sides, and also some white patches on the cheeks. You ask the daughter about this and she says that he has suffered from this since he has had a new filling put in. How do you know whether this is lichen planus?

What is lichen planus (LP)?

LP is thought to be an inflammatory disease that affects the upper dermis with destruction of the overlying basal layer of the epidermis. Looking more closely there is a dense infiltration of T-cells that is arranged in a band-like in appearance.

It is thought to be an autoimmune process, but the exact aetiology is unknown. The abnormal immune reaction can be provoked by a viral infection (such as hepatitis C) or a drug. The T-cells attack the body's own skin cells thinking that they are foreign.

It is important to note that longstanding LP can progress onto cancer. Squamous cell carcinoma can be seen in the mouth, vulval region or the penis.

Who does LP affect?

LP tends to occur most commonly over the age of 40. There are some contributing factors thought to be behind patients who suffer from LP. These are as follows:

  • a family history of LP
  • patients who have been under severe physical or emotional pressure
  • areas of skin injury known as an isomorphic response
  • isotopic response (to conditions like herpes zoster)
  • viral infection (as above, e.g. hepatitis C infection)
  • some drugs can cause an LP rash (e.g. gold, quinine)
  • rarely contact allergy

How common is LP?

Generally it is thought to be an uncommon skin complaint. It is thought to affect about 1% of the world’s population.

What are the clinical features?

LP can take several forms and it is important to be aware of these when making a diagnosis. It is important to note that scarring is permanent including loss of hair on the scalp.

Classical LP

Patients tend to have a number of shiny, flat- topped, firm papules on their skin. These papules are purple in colour and can present in a number of sizes, from small to large (over a centimetre). You should look for characteristic white lines (called Wickham's striae) that cross the papules. The configuration can be in lines (linear) or in rings. Remember to ask the patient if they are itchy as this is often the only sign. Look for the characteristic areas which are:

  • the front of the wrists
  • ...

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