Lentigines within nevus depigmentosus: a rare collateral effect of UVB therapy?

Nevus depigmentosus is an uncommon hypopigmented macule or patch that is congenital and stable in its relative size and distribution throughout life; it occurs sporadically and may be localized, segmental or, less often, systematized. We report the case of a 17-year-old girl with a segmental achromic nevus of the left leg and a patch on the lower back with late age of onset who developed lentigines after prolonged intense ultraviolet B exposure as a consequence of an incorrect diagnosis of segmental vitiligo.