These are usually present at birth, but may also develop within the 1st year of life. They most commonly present as a brown, tan or black pigmented patch, but may have multiple shades. There is usually increased hair growth within the CMNs, and this is especially prominent around puberty. Congenital melanocytic naevi are usually asymptomatic. They grow proportionately with the child and can be classified into small (<1.5cm), medium (1.5-19.9cm), and large (≥20cm) according to their estimated size in adulthood.

这是一种非癌症性皮肤病变，是由于皮肤最上层（也称为表皮）过度生长所致。一半的病变在出生时就已存在，另一半则在儿童时期发展。表皮痣通常呈线状，颜色为棕色或棕褐色。刚出生时，表皮痣通常是扁平的，但随着孩子的成长，表皮痣会变厚，变得粗糙/疣状。

咖啡斑表现为扁平、圆形或椭圆形的棕色斑块，最常出现在躯干和四肢。这些斑块可能在出生时就有，也可能在幼儿期出现。斑块大小不一，从几毫米到≥20 厘米不等。