Drug Induced SCLE
Subacute cutaneous Lupus Erythematosus is a chronic, nonscarring photosensitivity disease which can occur in drug-induced or non drug-induced variants. Females predominate, in a ratio of roughly 4:1, and some of these patients will go on to develop some of the signs of systemic lupus erythematosus. The clues for this patient were largely those of testmanship: it is in a photodistributed area, annular and I gave you the clue that it was caused by a medication. In my residency, we all got sick and tired of hearing "use all available clues", but in reality, that's what you should do for everything.
The meds most commonly associated with it are antihypertensives (particularly HCTZ) and antifungals, with terbenafine being the chief culprit.
Just as an aside, if you see a photodistributed rash, always biopsy it. It'll make your life so much easier, because 95% of the time you can cut to the chase with the diagnosis, especially if you combine it with serology and clinical examination. Serology in both "wild type" SCLE and drug induced often are Ro+, often ANA positive as well.
The ddx is pretty broad, if you just consider the papulosquamous nature of the rash, but if you do a biopsy, if you consider the distribution of the rash, and if you consider the serology you can nail it the vast majority of the time. For instance, some SCLE looks psoriasiform, but is photodistributed. That is unlike most psoriasis, right? Same with CTCL. It is unusual to get true papulosquamous CTCL in a photo distribution. GA, which is rarely photodistributed, is almost never papulosquamous, true? And acute LE patients are usually sick, which is unusual with SCLE.
For those of you who don't have access to Jerry Litt's manual, the Drug Eruption Reference Manual, please ask your docs to order one. It is immensely helpful in deciding which drugs cause which kind of eruption. If you've been to the AAD, Jerry will sign them, give you a copy of his poem he wrote for JAMA, I think called "A Hunk of Skin" which was, he told me, the second poem they ever printed, way back in the sixties. He is a spry old guy, and a lot of fun. For those of you who have had the pleasure of meeting Jerry, here's a little blast from the past: