Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 57 5 2019 09 30 335 337 EN Mohammad Ebrahimzadeh Ardakani Department of Dermatology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Narges Ghanei Department of Dermatology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Mitra Shafihosseini Department of Dermatology, School of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. 2018 06 14 2018 12 19 Unilateral Nevoid Acanthosis Nigricans (UNAN) is a rare, benign, autosomal dominant form of Acanthosis Nigricans (AN), which is a disorder of keratinization. Unlike AN, the lesions of UNAN are distributed unilaterally while the histopathological findings are similar to the common form of AN. The first description of UNAN was given by Krishnaram in 1991, and following that report, very few cases have been reported. Herein, we present another case of UNAN localized over the back, in a young adult female. https://acta.tums.ac.ir/index.php/acta/article/view/7315 https://acta.tums.ac.ir/index.php/acta/article/download/7315/5270