The correct answer is E. Fixed drug eruption.

This patient presents with fixed drug eruption (FDE), likely secondary to NSAIDs (such as ibuprofen or naproxen) which are often taken monthly for menstrual pain. FDE is characterized by one or few round, well demarcated erythematous patch or plaques at the same site upon re-exposure to the causative drug. The rash will often present 7-14 days after the first exposure but can present within 24-48 hours upon re-exposure. Other frequent culprits of FDE include sulfonamides, tetracycline, pseudoephedrine (non-pigmented FDE).

Nummular dermatitis: This condition presents as coin-shaped, pruritic, eczematous plaques that can occur anywhere on the body. It does not typically recur in the same location with a predictable pattern, nor is it associated with drug exposure.
Sweet’s syndrome: This is an acute febrile neutrophilic dermatosis characterized by painful, erythematous plaques or nodules, often accompanied by fever and leukocytosis. It does not present with recurrent lesions in the same location and is not typically drug-induced.
Erythema multiforme: This condition is characterized by targetoid lesions, often triggered by infections (e.g., herpes simplex virus) rather than drugs. It does not present with fixed, recurrent lesions in the same location.
Arthropod reaction: This refers to localized skin reactions to insect bites, which can be pruritic and erythematous but do not recur in the same location with a predictable pattern and are not drug-induced.
References:

Bolognia JL, Schaffer JV, Duncan KO, Ko CJ. Dermatology Essentials. 2nd ed. Elsevier; 2022.

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