In 1877, Dr Heinrich Koebner inflicted an experimental trauma on the uninvolved 
skin of a psoriatic patient. This resulted in the appearance of a typical 
psoriatic lesion at the site of trauma. This reaction, known as Koebner's 
phenomenon (KP), has subsequently been associated with several skin diseases. 
However, it has not been associated previously with necrobiosis lipoidica 
diabeticorum (NBL), a rare skin manifestation of diabetes mellitus. This report 
presents the unusual finding of NBL associated with KP in a patient with 
diabetes mellitus.