Becker melanosis was described in 1948 by S. William Becker in two young men with acquired melanosis and hypertrichosis in a unilateral distribution.  Since then, this condition has been termed Becker nevus.
The pathogenesis of Becker nevus remains uncertain.
Androgens may play a role in Becker melanosis, as evidenced by its peripubertal development, male preponderance, hypertrichosis, occasional development of acneform lesions within the patch, and rare association with accessory scrotum in the genital region. In addition, a significant increase in the number of androgen receptors in Becker melanosis lesional skin has been reported. 
A study of 19,302 men aged 17-26 years revealed a prevalence of Becker melanosis of 0.52%.
Males are affected by Becker melanosis more often than females.
Although Becker nevus usually is a sporadic condition that manifests in the peripubertal period, both congenital and familial cases  have been described.
Advise patients that Becker melanosis is a benign entity and does not require treatment except for cosmetic reasons.