DISCUSSION
The list of dark brown, round macules that come and go in the exact same locations is a short one—in fact, it only includes fixed drug eruption (FDE). This is a unique adverse reaction to one of several medications; common culprits are ibuprofen or other NSAIDs, aspirin, members of the sulfa family, penicillin, and several antiseizure medications.
The exact mechanism for this reaction is unknown, but it does appear to involve the localized production of cytokines. There is a range of morphologic presentations for FDE: some lesions are more targetoid than others; some are darker (especially in patients with darker skin) while others are more pink.
Furthermore, many patients develop additional lesions over time. A few, on the other hand, will reach a point at which they stop reacting to the offending product.
Of all the drugs causing FDE, sulfa-based products are among the more consistent offenders. Thus, we always ask about chronic urinary tract infections.
TAKE-HOME LEARNING POINTS
- Fixed drug eruptions (FDE) usually manifest with round, targetoid macules that are occasionally blistery.
- The lesions recur or darken with each “challenge” from the drug, which can be one of several potential offenders.
- The fact that the lesions keep recurring in the same location (ie, fixed) is pathognomic for FDE.
- FDE lesions can occur almost anywhere on the body—even on palms or soles.