简介：AbstractIntroduction:Nicolau syndrome is a rare complication following intramuscular injections of various drugs. It is characterized by severe pain, skin and sometimes muscle necrosis after drug injection. However the pathogenesis of Nicolau syndrome remains unclear.Here, we report a case of Nicolau syndrome following metamizole injection.Case presentation:A 35-year-old female presented with an painful necrotic ulcer who developed Nicolau syndrome after an intramuscular injection of metamizole in her right thigh due to reccurent episodes of back pain. This reaction is typical for Nicolau syndrome.Discussion:The most common finding of Nicolau syndrome in the early period was severe pain at the injection site. Other common findings were skin discoloration, tenderness, and swelling; indurated livedoid plaques; and erythematous, ecchymotic and purpuric patches. The histopathological results of the case with Nicolau syndrome showed formation of ulceration and fat necrosis.Conclusion:Although Nicolau syndrome is an uncommon cutaneous adverse reaction, clinicians should be aware of this complication to prevent or minimize the severity of Nicolau syndrome.