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Author: Dr Delwyn Dyall-Smith FACD, Dermatologist, 2010.
Oral lichenoid drug eruption is an uncommon medication-induced chronic change inside the mouth. It appears the same as idiopathic oral lichen planus clinically and under the microscope, but an oral lichenoid drug eruption resolves if the triggering drug is ceased.
An oral lichenoid drug eruption is predominantly a problem seen in adults, probably because adults are the most frequent users of the majority of medications associated with this reaction. However, it has also been reported rarely in children.
A clear temporal relationship between medication and lesion is not always obvious. The delay between starting the medication and developing the reaction (latent period) can be up to 2 years, although it is on average 1-2 months. And there have been reports of the lesion appearing only after the triggering medication had already been ceased.
Medications associated with this reaction include:
Oral lichenoid drug eruption is less common than lichenoid drug eruption of the skin and fewer drugs have been reported in association with the oral form.
The changes may be noticed coincidentally when your doctor or dentist is checking inside the mouth, but it may be associated with stinging/burning with hot or spicy foods or a roughness.
Clinically, oral lichenoid drug eruption looks the same as idiopathic lichen planus, with either the classic reticular (net-like) pattern or a predominantly erosive (ulcerated) form. One clinical clue that the problem is due to medication is that a drug eruption often only affects one side (unilateral).
It is seen most commonly on the buccal mucosa (inside cheeks) but also on the tongue, floor of mouth, palate or gums. There may also be a lichenoid drug eruption on the skin.
A biopsy will show basically the same changes as seen in idiopathic lichen planus although there may be some features that point the pathologist towards the diagnosis of a drug reaction rather than an idiopathic lichenoid condition. These include the distribution/pattern of the inflammation and the cell types present.
Patch testing may an additional test that can sometimes confirm the triggering drug, but false negatives are common.
Withdrawal of the drug resulting in resolution of the lichenoid reaction is an important diagnostic criterion. Recurrence of the reaction with drug re-challenge (provocation test) is the definitive test. Sometimes this happens inadvertently when a related medication is prescribed.
In consultation with the prescribing doctor, withdrawal of the trigger medication is the treatment of choice. Lesion resolution typically takes weeks to months, although there may be some milder persistent changes. However, it can sometimes be a challenge to identify the trigger drug as often the patient is taking multiple medications that have been reported to cause a lichenoid drug eruption, such as for the treatment of high blood pressure.
Sometimes the severity of the medical condition being treated is such that the doctor does not wish to cease the medication, e.g., imatinib mesylate for chronic myeloid leukaemia (CML) or gastrointestinal stromal tumour (GIST). Options for treatment then include:
It may then be possible to comfortably continue the trigger medication.
Good oral hygiene is important to prevent secondary infections such as oral candidiasis (thrush).
Temporary mucosal protectants such as milk of magnesia may give symptom relief.
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