Becker's nevus (BN) typically presents as an acquired hairy patch or plaque with somewhat increased smooth muscle, most likely the arrector pili muscles. Although BN is encountered commonly after puberty, considering its hamartomatous nature of BN, it is more rational that BN might develop at early childhood or even at birth.
In the pathogenesis of BN, androgens may play a role, as evidenced by its 'peripubertal' development, male preponderance, hypertrichosis, occasional development of acneiform lesions within the patches, and increase in the number of androgen receptors in BN lesional skin. BN becomes hairy and darker under the influence of androgens, and thus more visible, during and after puberty.