Afatinib-Induced Acneiform Eruption in EGFR Exon 21 L858R-Mutant Stage IVA Lung Adenosquamous Carcinoma: Dermoscopy-Supported Diagnosis and Complete Resolution Fifteen Days After Drug Withdrawal

Abstract

Background: Acneiform eruption is a monomorphic inflammatory disorder of the pilosebaceous unit that resembles acne vulgaris but characteristically lacks comedones; drug reactions, particularly to epidermal growth factor receptor (EGFR) inhibitors, are its commonest trigger.

Objective: To describe the clinical course, bedside diagnostic reasoning and outcome of an afatinib-induced acneiform eruption documented by serial photography, dermoscopy and potassium hydroxide microscopy.

Case Presentation: A 59-year-old man with stage IVA adenosquamous carcinoma of the left lung harbouring an EGFR exon 21 leucine 858 to arginine (L858R) mutation developed erythematous papules and pustules on the face, neck, chest and back three days after his first dose of oral afatinib 40 mg daily, and was referred on day 21 with intense pruritus, burning and adherent nasal crusting. Examination showed discrete follicular papules and pustules with crusting and no comedones at any site. Dermoscopy demonstrated folliculocentric papules without comedonal plugging, and 10% potassium hydroxide microscopy showed no hyphae, mites or lice, excluding Malassezia folliculitis and demodicosis. Naranjo scoring yielded 7 points, indicating a probable adverse drug reaction. Afatinib was withdrawn and oral doxycycline 100 mg twice daily for two weeks, as-required cetirizine, saline compresses followed by clindamycin 1% lotion, hydrocortisone 2.5% cream, emollient and photoprotection were given. Pustules and crusts cleared by day nine and the eruption resolved completely fifteen days after withdrawal, leaving post-inflammatory hyperpigmentation.

Conclusion: Recognising the monomorphic, comedone-free morphology and its temporal link to the drug permits accurate bedside diagnosis, while prophylaxis begun with the inhibitor may avert withdrawal of effective targeted therapy.