LP-Like Drug Eruptions
These have been reported with a large number of medications. Thiazide diuretics, gold, antimalarials, ^-blocking agents, vitamins, and NSAIDs are among those most commonly cited. This differential must be carefully evaluated in every case of LP. Some reactions are clinically identical to idiopathic LP; however, subtle findings on routine biopsy may help to distinguish them. Immunopathology is not helpful. LP-like drug reactions resolve slowly and require a good deal of support and confidence on the part of the treating practitioner. Clinical features that help to distinguish the two include a photodistribution and a psoriasis-like appearance common with the drug-induced form.
Rarely cases are encountered where these two disorders seem to merge. In most instances, a biopsy combined with direct immunofluorescence will distinguish between them. Most cases turn out to be chronic discoid lupus. Rare overlap cases do occur.
Exanthematic LP without pruritus may be difficult to separate from a generalized papu-losquamous syphilid. The latter is associated with lymphadenopathy and constitutional symptoms. A syphilis serology with precautions regarding prozone effect is definitive.
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