Lichenoid drug rash

What is a lichenoid drug eruption?

Lichenoid rashes are rare skin rashes that can be induced by many environmental agents, medications, or industrial by-products such as inhaled particles. the eruption from a lichenoid drug rash can sometimes be difficult to distinguish from idiopathic lichen planus due to similarities in clinical appearance and pathology seen on the skin biopsy.

Who gets a lichenoid drug rash?

Many medications have been reported in association with lichenoid drug eruptions, but often the time between the initiation of the medication and the appearance of the eruption (the latent period) can be long, more than a year in some cases. In general, the latency period is 2 to 3 months (although this can vary for different drugs) and has even been reported to develop after the drug has stopped. This can make it difficult to identify the culprit drug.

Medications commonly reported to trigger a lichenoid drug rash include:

• Antihypertensive: ACE inhibitors, beta blockers, nifedipine, methyldopa
• Diuretics: hydrochlorothiazide, frusemide, spironolactone
• Non-steroidal anti-inflammatory drugs (NSAID)
• Phenothiazine derivatives
• Anticonvulsants: carbamazepine, phenytoin.
• Medicines to treat tuberculosis.
• Antifungal drug - ketoconazole
• Chemotherapeutic agents: hydroxyurea, 5-fluorouracil, imatinib

• Antimalarial agents such as hydroxychloroquine.

• Sulfa medications, including the hypoglycemic agents sulfonylurea, dapsone, mesalazine, sulfasalazine

• Metals - gold salts
• Others: allopurinol, iodides and radiocontrast media, interferon-a, omeprazole, penicillamine, tetracycline

Other medications that have been reported in association with lichenoid drug eruptions include:

• Tumor necrosis antagonists of factors such as infliximab, etanercept, and adalimumab
• Imatinib Mesylatetyrosine kinase inhibitor)
• Misoprostol (prostaglandin E1 agonist)
• Sildenafil citratus (Viagra ™)
• Vaccines (especially those of Herpes zoster and the flu).

If a lichenoid rash has turned into a drug, it is quite possible that the same reaction will appear more quickly after exposure to another drug from the same family. Reported examples have included proton pump inhibitors (for dyspepsia) and HMG-CoA reductase inhibitors (for high cholesterol)

What are the clinical features of a lichenoid drug rash?

Lichenoid drug eruptions can be very similar to those of idiopathic lichen planus, although there may be features that can help distinguish them, which may include:

• Extensive skin rash distributed symmetrically on the trunk and extremities.
• Photodistribution: the rash is predominantly in areas exposed to the sun
• The rash may be scaly resembling eczema or psoriasis
• Wickham striae are generally absent
• Nail and mucous membrane involvement (eg, mouth) is rare (oral lichen planus)
• More likely to mark pigmentation after the active rash has disappeared.

How is a lichenoid drug rash diagnosed?

The diagnosis can be suspected from the unusual clinical features, and a skin biopsy is then taken. The pathological features of a lichenoid drug eruption may be difficult to distinguish from idiopathic lichen planus, but the type of eruption may be suggested by the types and distribution of inflammatory cells, as well as other changes.

A detailed history of medications taken in the past year, including those taken only briefly (or even just once), can help identify the culprit.

Sometimes patch Testing with the drug can confirm identification, but false negatives are common.

A "challenge test" involves deliberately re-administering the drug to the patient in the hope that the rash will reappear, but more quickly. Sometimes this happens unintentionally when another member of the same class of drugs is given to treat the original medical problem, or the same drug is given for a different problem.

Discontinuation of the suspected drug with resolution of the rash is generally taken as confirmation of the diagnosis and drug trigger.

What is the treatment for lichenoid drug rash?

The trigger medicine should be stopped and the rash should improve, although it may take weeks or months to clear up. Commonly flat pigmented Freckles persist and fade more slowly. Nail disease will take six months or longer to clear up, although gradually spreading improvement can be seen during this time.

Sometimes the drug cannot be discontinued due to the significance of the underlying medical condition compared to the rash, e.g. Eg imatinib for chronic myeloid leukemia or gastrointestinal stromal tumor. The dose can be reduced or continued unchanged and the rash can be treated with current steroid cream or, if it is very extensive and severe, oral corticosteroids such as prednisone or prednisolone. Steroids can provide good relief or even resolution.