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Cutaneous adverse reactions to medications are common; many are non-immunological in nature. This quiz considers some drug eruptions believed to be immunologically-mediated ('drug allergy'), or that are at least idiosyncratic in nature.
Often it is difficult to be certain whether a rash is due to drug, a skin disease or an underlying illness. A careful drug history is essential, considering prescription and over-the-counter medicines, topical agents, herbal remedies and supplements. Previous exposure, dose, duration and frequency of drug administration should be established. Refer to standard textbooks and obtain specialist advice from a dermatologist as necessary.
For each of the ten cases, study the image(s) and then answer the questions. You can click on the image to view a larger version if required.
Each case should take approximately 2 minutes to complete. There is a list of suggested further reading material at the end of the quiz.
When you finish the quiz, you can download a certificate.
Name this skin condition.
Lichenoid drug eruption in patient taking several possible precipitants
What are its clinical features?
Lichenoid eruptions are rarely recognised as being due to a drug as they are of slow onset and slower resolution. They are given the name 'lichenoid' because histologically they resemble lichen planus. They may also resemble lichen planus clinically. The primary pathological event appears to be an autoimmune attack by T cells on the epidermis.
There is a symmetrical eruption of indurated papules and plaques that may have a dry or scaly surface. Mucosal involvement is uncommon. Lichenoid eruptions may be asymptomatic but are often extremely pruritic. Postinflammatory pigmentation is usual and scarring may occur. Sometimes the eruption is confined to areas exposed to the light (photosensitive lichenoid eruption). This is characteristic of quinine reactions.
Management may require systemic steroids and antimalarials (if they haven't caused the eruption).
List drugs that are commonly responsible.
Causes include antimalarials, beta blockers, ACE inhibitors, calcium channel blockers, thiazides, antipsychotics, statins, proton pump inhibitors and many other medicines. Identifiying the causative drug may be very challenging as many affected patients are on several potential drugs and none of them have been recently introduced.