The correct answer is discoid lupus (choice “d”), which is generally confined to sun-exposed areas, tends to be chronic, and eventually causes scarring. Psoriasis (choice “a”) was unlikely, given the lack of corroborative findings over an extended period and the negative personal or family history—and because scarring would be quite unusual with that disease.
Basal cell carcinoma (BCC; choice “b”) is an unlikely choice because it is usually accompanied by significant sun damage and it does not typically wax and wane. Actinic keratoses (choice “c”) can come and go, but as with BCC, it would almost certainly be seen in the context of more widespread sun damage on the face.
A 3-mm punch biopsy was performed to confirm the diagnosis and rule out the other items in the differential. Discoid lupus erythematosus (DLE) usually demonstrates a classic set of histologic findings, confirming this common—and usually benign—form of lupus that favors the nose, ears, and neck but can be seen on any chronically sun-exposed area. Cancer/precancerous skin changes were definitely worth considering, given the chronicity of the condition.
Although DLE is quite common, outside dermatology it is seldom diagnosed initially. Instead, the natural inclination is treat the condition as “some sort of infection.” DLE often presents with annular, scaly lesions. This is potentially misleading, unless you look for two particular features (both of which, alas, were missing in this case!): The lesions often demonstrate atrophic, whitish centers, and when the scale is gently peeled off the lesions, you can see that the scale was plugging the follicular orifices, in effect dilating them.
Since systemic lupus erythematosus (SLE) can present with lesions of DLE, the initial labs should include an antinuclear antibody test. Approximately 5% of purely cutaneous DLE will evolve into SLE. The more extensive and serious the discoid eruption, the more likely is the presence of SLE.
DLE can also involve the scalp, where it can eventuate in focal or widespread scarring alopecia. Less often, it is seen on the lips, tongue, or other areas of oral mucosa.
With early, mild cases of DLE, better sun protection and topical steroid creams are all the treatment needed. But in more advanced cases involving scarring, oral therapy with hydroxychloroquine (6.5 mg/kg) is also necessary—assuming results of baseline lab testing (eg, comprehensive metabolic panel, complete blood count) and ophthalmologic examination are normal.
After three months of therapy with hydroxychloroquine (200 mg bid), this patient’s condition improved dramatically. The dosage was then reduced to once daily for another three months, at which point she’ll stop. She will repeat her eye exam and blood work at that time and continue to use sun protection, since the potential for recurrence is high.