Segmental Erythema Multiforme: An Unusual Drug Reaction to Anastrozole

Area of Science:

• Dermatology
• Oncology
• Pharmacology

Background:

• Erythema multiforme (EM) is an immune-mediated mucocutaneous hypersensitivity reaction.
• Anastrozole, a nonselective aromatase inhibitor, is used in breast cancer management and has known cutaneous side effects.
• EM is a rare side effect of anastrozole, typically presenting in major or minor forms with target lesions.

Observation:

• A patient developed segmental erythema multiforme.
• The reaction was localized to the cancer-affected breast area.
• The adverse drug reaction occurred months after initiating anastrozole therapy, contrary to the typical presentation of days.

Findings:

• This case highlights an extremely rare cutaneous adverse effect of anastrozole: segmental erythema multiforme.
• The localized presentation to the cancer-affected breast is highly unusual.
• The delayed onset of the drug eruption challenges conventional understanding of anastrozole-induced reactions.

Implications:

• Dermatologists should consider localized cutaneous adverse effects, including segmental EM, in patients undergoing anastrozole therapy for breast cancer.
• The findings suggest that anastrozole-induced hypersensitivity reactions can manifest with delayed onset and unusual localization.
• This case broadens the spectrum of known cutaneous side effects associated with aromatase inhibitors.