This patient likely has a fixed drug eruption (FDE). A painful purple patch that occurs in the same location repeatedly is a classic sign of a FDE. Patients with an extensive eruption may have central bullae that occur in the same location (fixed) each time the patient is exposed to the same medication. Lips, genitals, and hands are commonly involved. There may be only one spot with the first exposure; but if reexposed, the lesion may recur along with new areas. Common drug culprits are over-the-counter medications such as NSAIDs, pseudoephedrine, sulfonamide medications, and other antibiotics. The patient's periodic recurrent lesion is likely associated with his periodic use of ibuprofen. Drug discontinuation is the appropriate treatment, with resolution of the rash expected to occur over days to weeks.
Contact dermatitis is a delayed hypersensitivity reaction to a specific chemical. With repeated exposure to the chemical, a diffuse, pruritic eczematous dermatitis develops on the area that was exposed. The characteristic rash is typically reddish, scaly, and crusting, and when occurring on the penis may be associated with condom use. However, this patient's rash is not typical for eczematous dermatitis.
Herpes simplex virus infection usually presents with a vesicular rash if acute or erosion if chronic, as may be seen in patients with HIV infection. Recurrent genital herpes is similar to oral herpes with a prodrome, followed by grouped vesicles on an erythematous base, erosions, and crusting. This patient's presentation is not consistent with recurrent herpes simplex virus infection.
Primary syphilis presents as a chancre, classically a shallow nonexudative ulcer with an indurated border that is not painful. This patient's lesion is not consistent with a chancre.
