Erythema multiforme major triggered by salvage radiotherapy for prostate adenocarcinoma

Erythema multiforme (EM) is a hypersensitivity reaction most commonly triggered by viral or bacterial illness, or by medications, including antibiotics, anti-epileptic drugs and nonsteroidal anti-inflammatory drugs. We present a rare case of EM major, with onset shortly upon completion of a course of external beam radiotherapy for relapsed prostate cancer in the absence of any other identified triggers.