Linear congenital Becker nevus.

Becker nevus is an acquired disorder that usually manifests in late childhood or adolescence as a hyperpigmented hypertrichotic patch usually located on the upper trunk or proximal upper extremities. Only a few cases of congenital and familial Becker nevus have been described. Although the lesions may have various shapes, they consistently have a geographic or blocklike configuration in an irregular fashion; a linear pattern has rarely been reported. We describe a case of linear congenial Becker nevus following Blaschko line that appeared at birth on the right shoulder, with hypertrichosis developing 4 years later.