There are a number of different conditions that can cause white lesions in the mouth. Some conditions like oral candidiasis (mouth thrush) are among the more common causes while others like leukoplakia and lichen planus are less often seen. Many people do not understand the differences between these conditions and despite the similarity of symptoms these diseases may have little else in common.
What is lichen planus?
Lichen planus is a condition where there is inflammation on areas of the skin and mucous membranes lining the cavities thereby causing lesions ranging from purple to white. It can cause pain in the mouth and itching on the skin. The exact cause is unknown but it appears to be triggered by certain viral infections. It can last for months to years and then resolve spontaneously although certain medication can help to relieve symptoms and hasten healing.
There is a small risk of cancer among men who have oral lichen planus and it may also increase the risk of skin cancer in some people but this is rare. Lichen planus affects about 1 in 100 people in the United States. It can affect any age group but is more commonly seen in people of 30 to 60 years of age. Men and women are affected equally. Although it is not a seasonal condition, lichen planus seems to be more common during December and January in some areas.
Causes of Lichen Planus
The immune system defends the body against foreign threats like microbes. Sometimes it can turn against the body’s own tissues and attack it. As a result inflammation may arise. In lichen planus this type of cell-mediated immune response occurs at certain sites on the skin and mucous membrane of the mouth, penis or vagina. The exact reason why it occurs is unclear.
It appears there are certain triggers and a genetic predisposition has been postulated due to the frequency of genes like HLA-B7 in affected families. Although many of the triggers are viral infections, it does not mean that lichen planus is an infection. Instead the body’s immune response to these viruses may in some way be altered that it then attacks its own tissues. Trigger viral exposure includes hepatitis C infection, hepatitis B vaccine and the flu vaccine.
Certain substances have also been implicated as triggers. This includes drugs like ibuprofen and naxopren as well as certain medication for arthritis, heart disease and hypertension (high blood pressure). Other non-pharmaceutical chemicals have also been considered such as certain pigments and metals. Similarly there may be a host of other triggers that have not as yet been identified.
However, it is possible for lichen planus to occur despite the lack of any known trigger factors. In fact prior hepatitis C infection is seen in less than 20% of cases.
Symptoms and Pictures
Lichen planus presents with cutaneous (skin) lesions and mucous membrane lesions (mouth, vagina and penis).
Lichen planus on the skin presents as itchy lesions, that are red to purple in color and flat. It more commonly arises on the folds (flexures) of the limbs such as the wrist and ankles. There may also be blister formation with scabs and crusts.
Lichen planus lesions can also occur on the scalp and nails where it may result in hair loss and nail deformity/loss respectively.
Mouth lesions of lichen planus appear as gray to white spots and patches. Sometimes there may be burning or even pain at these lesions but often there are no further symptoms. These lesions may be seen on the gums, inside the cheeks, lips or tongue.
Mouth lesions may not necessarily be present with skin lesions as well.
Diagnosis of Lichen Planus
A punch biopsy may be necessary to diagnose lichen planus. A small sample of the lesion along with underlying tissue is collected and then examined under a microscope. There are certain cellular changes that are seen which is characteristic of lichen planus. Additional hepatitis C tests may be done to verify whether a person had hepatitis C in the past or not, as this is a known common trigger.
It is important to note that there are other skin and mouth conditions that can appear in a similar way to lichen planus. Therefore further diagnostic investigations are necessary so that the appropriate treatment can be prescribed once the diagnosis is confirmed. Differential diagnosis which are those conditions that may resemble or be mistaken for lichen planus include guttate psoriasis, lichen simplex chronicus, oral candidiasis and oral leukoplakia.
Cancer Risk with Lichen Planus
The oral (mouth) lesions of lichen planus has the potential to become cancerous (malignant). There may also be an increased risk of squamous cell carcinoma with skin and vulvar lesions but this is rare. The malignant potential of mouth lesions are uncommon and more frequently seen among males. It is more likely to occur in oral lichen planus lesions that are ulcerated (open sores).
Treatment of Lichen Planus
The skin lesions can resolve within months while the mouth lesions may take several years. About half of all cases of cutaneous (skin) lichen planus will resolve within 6 months and approximately 85% resolve within 18 months. Oral (mouth) lesions may take up to 5 years or more to resolve. Sometimes this resolution is spontaneous while at other times treatment is necessary.
Treatment for lichen planus includes:
- Corticosteroids to suppress immune activity and reduce inflammation. These drugs are commonly prescribed but only for the short term.
- Retinoids help to increase the turnover of surface cells thereby making lesions on it less adherent. However, these drugs are associated with severe side effects and not the first choice for treatment.
- Immunosuppressants like cyclosporine suppress the immune system as the name suggests. It is only considered when other drugs fail to act.
- Antihistamines may help reduce the inflammation and ease symptoms like itching but cannot treat the lichen planus.
- Light therapy (phototherapy) using UVA (ultraviolet A) or UVB (ultraviolet B) is also effective for the treatment of lichen planus.
Recurrence is uncommon with skin lesions once it has spontaneously resolved or effectively treated. However, recurrence is more common with mouth lesions which are often more difficult to treat.