Abstract
Nicolau syndrome (NS) is a rare and unpredictable adverse reaction that can occur after the administration of certain medications. A 9-year-old girl, accompanied by her father, visited the outpatient dermatology clinic with complaints of wounds on both upper arms. Upon reviewing her medical history, it was discovered that she had been receiving leuprolide for precocious puberty, and the symptoms began after the last two injections. The patient experienced pain during the leuprolide injection, and redness and swelling were noticed in the injection area on the same day. A few days later, the redness turned into ulcers. The fact that the development of NS cannot be detected in advance and the risk of rapid progression of tissue necrosis make disease management difficult. The prognosis of NS significantly depends on the patient, and when a developing lesion is noticed early, it is crucial to minimize the risk of complications.