An acquired, sharply demarcated, brownish patch with geographical borders and hypertrichosis is characteristic.
Occurs in about 0.5% of adolescent boys and young men.
The male to female ratio is approximately 5:1.2
A target tissue increase in androgen receptors or sensitivity to androgens may be responsible for the process.
Histopathological findings include elongation of rete ridges, hyperpigmentation of the basal layer, acanthosis, and hyperkeratosis.
Nevus cells are absent in the dermis, therefore malignant transformation is not a concern.
Typically begins in the second decade of life.
Begins as a circumscribed brownish macule or patch that gradually enlarges in an irregular fashion.
Hypertrichosis develops a few years after the pigmentation in the region of the pigmentation.
Hairs become coarser and darker with time.
BN is typically asymptomatic and unilateral.
Commonly located in the shoulder and upper chest.
Usually an acquired disorder, but congenital and familial cases have been described.
Occasionally associated with breast hypoplasia, hamartomas, lipoatrophy, and musculoskeletal anomalies.
When associated with noncutaneous anomalies, ref2242ed to as Becker nevus syndrome.
Except for cosmesis,
No treatment is necessary, except for cosmetic problem.
Hyperpigmentation can be treated with lasers, and hypertrichosis can be treated with depilation.