Psoriasiform Drug Eruption to Finasteride: Uncommon Side Effect of a Commonly Used Drug

A 25-year-old male developed an extensive psoriasiform eruption within 5 days of starting finasteride 1 mg daily for androgenetic alopecia. The patient presented with pruritic, erythematous, scaly papules and plaques on various parts of his body, excluding mucosa and genitals. Laboratory tests were normal, and a skin biopsy confirmed a psoriasiform drug eruption. The patient stopped finasteride and was treated with topical steroids and antihistamines, leading to complete resolution of the rash within 3 weeks. This case highlights the rare but significant cutaneous adverse effects of finasteride, emphasizing the need for clinicians to be aware of such potential reactions.