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This type of nevus, or birthmark, appears as a large dark discolored patch on the body. To some, a Becker nevus is considered a late-onset birthmark as it tends appear or become prominent around puberty. The most common location for this birthmark is on the the shoulder or back, but can really appear almost anywhere on the body. “The pigmented skin becomes thickened, and can also grow hair within the affected skin,” notes Dr. Adam Mamelak, a board certified Dermatologist in Austin, Texas. “Acne can also sometimes develop in and have a predilection for the affected skin.”
“Becker Nevus is most common in males, especially around puberty,” says Dr. Mamelak. There isn’t exact reasoning as to why it happens or why it appears around puberty, but it has been suggested that circulating testosterone may have a part in its formation. While it is possible for females to have this type of nevus, it is predominantly found in males.
“The overgrowth of the epidermis, pigment cells, and hair follicles are involved in the formation of the Becker Nevus,” states Dr. Mamelak. “The overgrowth of pigment cells is why this birthmark is also sometimes referred to as Becker melanosis.” This is not the type of skin disorder that is caught or that you get from interaction with another person or thing. “It is even unknown as to whether this nevus has a genetic link,” adds Dr. Mamelak. “We consider it to occur sporadically, but cases where these birthmarks run in families have been described.”
Overall, there is no good evidence that a Becker nevus increases one’s risk for cancer or any other disease. The only effect of this nevus is that it changes the thickness and pigmentation of the skin, not necessarily harming the body. Lasers can effectively treat both the pigmentation and to reduce hair in the area. Acne lesions will typically respond to OTC or prescription medications.
Rarely, this birthmark can be associated with other physical exam findings, including extra smooth muscle fibers in the affected skin. This accounts for the affected skin feeling tougher than the normal surrounding skin. An under- or over-development of underlying muscles, glands, limbs and/or appendages can also be noted. When a constellation of these other changes are observed along with the Becker Nevus, it is referred to as Becker Nevus Syndrome.