We describe a case of sex reassignment surgery and the subsequent development of lupus erythematosus tumidus (LET). LET is characterized clinically by erythematous, succulent, edematous, nonscarring plaques in sun-exposed areas. Results of histological examination show perivascular and periadnexal lymphocytic infiltration and interstitial mucin deposition. This report emphasizes that environmental triggers, including prolonged exposure to significant doses of estrogens as part of sex reassignment surgery, may lead to the development of lupus in a nonpredisposed individual.