Reverse Koebner phenomenon in erythema nodosum leprosum.

Background: Erythema nodosum leprosum (ENL) is an immunologically mediated phenomenon complicating the course of leprosy. Reverse Koebner phenomenon is the term used to describe the sparing of previously injured or diseased skin by new skin lesions of the disease.
Methods: A middle-aged woman with a known case of lepromatous leprosy for the past year presented with an eruption of reddish painful nodules over her body. The lesions were found to characteristically spare the sites of previous scars.
Results: This sparing phenomenon of previous scar sites has been termed reverse Koebner phenomenon, a site of the body that offers greater resistance than the rest of the body to the onset of the disease, seen in various diseases, but it has never been described in ENL.
Conclusion: This sparing of scar sites in ENL can be attributed to reverse Koebner phenomenon.
(© The Author(s) 2023. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene.)