Nevus spilus appearing at birth as multiple congenital melanocytic nevi.

Abstract

The age of onset of nevus spilus (NS) is a debated topic (1, 2), made problematic by the fact that NS is an entity consisting of two elements, the melanocytic nevi and the hyperpigmented patch on which they insist; the patch becomes more visible with time and may not be clinically evident in early epochs of life. What will become a NS at birth may have the classic features of more or less extensive, often segmental hyperpigmented patch, on which melanocytic nevi of variable diameter stand up or can present as an isolated hypermelanic patch or as congenital melanocytic nevi unusually located on a segment of apparently normal skin or finally may be not at all obvious. In the subsequent months the hypermelanic patch becomes evident and darkens gradually, but its shape and extension do not change. Therefore, the hyperpigmented patch can go from a complete invisibility to a brown light or dark brown discoloration: the patch only changes in color intensity, which generally increases with time, its shape remains unchanged, while adjusting its size to that of the segment of skin on which it stands, does never gets raised and is not associated with hypertrophy of the hair. On dermoscopic examination the patch shows in some cases a uniform hyperpigmentation with more marked rhomboidal design, in other cases a net, globular or parallel melanocytic pattern; the uniform hyperpigmentation and the melanocytic pattern can be combined in different areas of the same NS. The hyperpigmented patch should be considered as optional clinical expression of a postzygotic mutation in the genes that predispose to the onset of nevi.