[A man with erythematosquamous plaques]. / Een man met erythematosquameuze plaques.

A 43-year-old male visited our dermatology department with a skin eruption diagnosed as psoriasis. It began 1 month after starting peg-interferon-α-1a therapy for multiple sclerosis. Peg-interferon is known to be able to induce psoriasis, as well as other medication, while the pathophysiology remains unclear.