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Genetic and Rare Diseases Information Center (GARD)

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Becker's nevus

Other Names for this Disease
  • Becker melanosis
  • Becker naevus
  • Becker nevus
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Your Question

I have Becker's nevus on the top of my right pectoral. I'm heavily into fitness and weight lifting. I've noticed that it is impossible for me to develop an even chest. Muscle seems to not grow where my nevus is located. Does Becker's nevus prohibit muscle development? Does the nevus affect me in that manner, and if so, is there any way to fix this?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What are the signs and symptoms of Becker's nevus?

A Becker's nevus typically begins to develop during childhood or adolescence on the shoulder or upper trunk, although it may develop on other areas of the body.[1] Pigmentation may be subtle at first, but the nevus typically expands during the first several years.[2] The resulting birthmark is usually large, brown, and on only one side of the body. Sometimes it may cover over half of the upper back or chest. After puberty, the nevus often darkens and becomes hairier than the surrounding skin (hypertrichosis). In some individuals, acne may develop within the nevus.[1]

Rarely, there may be abnormalities of underlying tissues associated with the nevus, such as ipsilateral breast hypoplasia (underdevelopment of the breast on the same side of the body as the nevus). When this occurs, it is sometimes known as Becker nevus syndrome, a type of epidermal nevus syndrome.[1] In addition to the nevus, individuals with Becker nevus syndrome may have various skin-related (cutaneous), muscular or skeletal abnormalities.[1][3]
Last updated: 4/25/2012

What is Becker nevus syndrome?

Becker nevus syndrome is characterized by the presence of a Becker nevus in association with underdevelopment (hypoplasia) of the breast or other skin-related, muscular, or skeletal defects, all of which usually involve the same side of the body as the nevus (ipsilateral).[3] Specific signs and symptoms in addition to the nevus may include ipsilateral breast hypoplasia; skeletal abnormalities such as hypoplasia of the shoulder girdle, scoliosis, fused ribs, and ipsilateral shortness of the arm; and several other features.[4][3] The condition is thought to be sporadic (occurring in individuals with no history of the condition in the family).[3] Treatment varies depending upon the specific symptoms present and the extent of the condition in the affected individual.[4]
Last updated: 4/25/2012

What are the signs and symptoms of Becker nevus syndrome?

Becker nevus syndrome is characterized by the presence of a Becker nevus in association with underdevelopment (hypoplasia) of the breast and/or other skin-related (cutaneous), muscular, or skeletal defects, all of which usually involve the same side of the body as the nevus (ipsilateral).[3] Breast hypoplasia affects both males and females, but is more noticeable in females.[4] Other muscular and skeletal abnormalities may include absence of the pectoralis major muscle (pectoral); underdevelopment of the muscles of the shoulder girdle; abnormal curvature of the spine (scoliosis); vertebral defects; fused ribs; ipsilateral shortness of a limb; underdevelopment of the teeth and jaws; a "sunken chest" (pectus excavatum) or abnormally prominent chest (pectus carinatum); and other findings.[4][3] Extra (supernumerary) nipples and abnormally sparse hair under the armpit on the affected side of the body have also been reported in some affected individuals.[4]
Last updated: 4/23/2012

Is there a way to treat breast hypoplasia or improve chest muscle development in individuals with Becker's nevus or Becker nevus syndrome?

There is limited information in the available medical literature about treatment for breast hypoplasia or underdeveloped chest muscle(s) in affected individuals. We were unable to find literature specific to treatment of hypoplasia or aplasia of the pectoralis muscles in affected individuals.

It has been proposed that spironolactone, a medication that has been used in dermatological therapy to treat acne, hirsutism and androgenic alopecia, may improve breast hypoplasia in affected individuals.[5] The authors of a study evaluating the effect of spironolactone on a female patient with Becker's nevus with ipsilateral breast hypoplasia reported that after one month of administration of spironolactone, breast enlargement was seen in only the hypoplastic breast with Becker's nevus.[6] It should be noted, however, that there have been several reports in the literature of gynecomastia (excessive development of breasts in males) occurring in individuals treated with spironolactone for dermatological purposes.[6]
Last updated: 4/25/2012