A diagnostic challenge: acute generalized exanthematous pustulosis or pustular psoriasis due to terbinafine

Summary A 72‐year‐old man developed a generalized erythematous pustular eruption 11 weeks after commencing terbinafine. Clinically and histologically, the appearance was that of acute generalized exanthematous pustulosis (AGEP), and the disease was managed with topical preparations. Initial improvement was marred by relapse of acute pustulosis, now more in keeping with terbinafine‐induced pustular psoriasis (PP), which was successfully treated with acitretin. This case highlights the difficulty of differentiating between AGEP and PP.