The simultaneous occurrence of a patch of light or dark brown hyperpigmentation with hypertrichosis (Becker's nevus) together with (usually ipsilateral) soft tissues hypoplasia (especially breast, in women) and underlying skeletal anomalies (i.e., vertebral hypoplasia, scoliosis, pectus carinatum or excavatum) represents the Becker's nevus syndrome (BNS) phenotype. It was first described (as a single cutaneous lesion) by Becker in 1949 and then associated with the surrounding musculoskeletal disorders. The syndrome has also been reported as pigmentary hairy epidermal nevus syndrome. Less than 100 cases have been reported in the literature, with a slightly higher incidence in females and only few familiar cases: paradominant postzygotic mutations and/or an androgen-dependent hyperactivation have been reported as the causes of the diseases.The extracutaneous lesions are congenital and nonprogressive, and the natural history of the Becker's nevus is the same as that of isolated nevi: in prepubertal boys, the pigmentation may be less intense and the hairiness may be absent or mild, as occurs in women, whereas in men, there is an increase of hairiness after puberty. The treatment is essentially cosmetic, and potential therapeutic options include electrolysis, waxing, makeup, or laser.