Hypertrichosis over 
a brown patch

A Becker nevus, also referred to as Becker melanosis, is a single, benign brown-colored skin lesion that most commonly appears in peripubertal boys and can be considered a late-onset epidermal nevus. It can principally be defined by the time of...

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A Becker nevus, also referred to as Becker melanosis, is a single, benign brown-colored skin lesion that most commonly appears in peripubertal boys and can be considered a late-onset epidermal nevus. It can principally be defined by the time of onset of the lesion and the pronounced hypertrichosis.


The pigmented lesion that is characteristic of Becker nevus appears as a unilateral patch, typically on the chest or back area. Initially, this patch will be lighter in color.¹However, as the patient nears puberty, it is thought that the increase in circulating androgens plays a role in activating the gene that leads to the development of a progressively darker patch and the characteristic hypertrichosis.²

The growth of the hairs on the patch usually occurs several months after the patch darkens. These hairs are typically brown or black, regardless of the individual’s hair color. The border of the pigmented lesion is typically irregular and will appear to be composed of many macules blending together. The upper trunk is by far the most common location of a Becker nevus. However, there are reports of cases of Becker nevus occurring on virtually any part of the body.³

These lesions are also often accompanied by small areas of acne within the patch, but this is neither a requirement nor particularly notable, except for the link to the role of androgens. The patch that develops is an amalgamation of over-development of the epidermis and over-expression of both hair follicles and melanocytes.³

Typically, individuals will only have one Becker nevus that will remain for the duration of their lives with minimal decrease in pigmentation. It is painless, but many patients consider the lesion cosmetically displeasing. Having a Becker nevus has not been shown to predispose individuals to development of any particular disease. In addition, the development of a Becker nevus is not thought to be hereditary, so it may not be present in any other members of the patient’s family. 


Smooth muscle hamartomas are often associated with a Becker nevus. Additionally, muscular tissue hypoplasia has been associated both in areas around and under a Becker nevus. When a Becker nevus exists in association with hypoplasia of the ipsilateral pectoralis muscle, ipsilateral limb shortening, adrenal hyperplasia, spina bifida, scoliosis, or accessory scrotum, it is termedBecker nevus syndrome.^3,4 This term indicates that ectodermal anomalies extend beyond just the skin and include other ectoderm-derived structures.

Becker nevus syndrome is much more common in women, when compared with Becker nevus that is not associated with abnormalities, which displays a strong male preference. The male-to-female ratio in Becker nevus syndrome is 2:5, whereas a 6:1 male-to-female ratio is seen in Becker nevus.³

The differential diagnosis of a Becker nevus includes a café-au-lait macule, a congenital melanocytic nevus, erythema dischromium perstans, plexiform neurofibromas, and smooth muscle hamartomas. Often lichenified skin is considered a part of the differential as well. Clinical assessment of the timing of the pigmented patch, lack of association with scratching, absence of clear genetic link, and presence of hypertrichosis can be helpful. 

Although a Becker nevus is typically a clinical diagnosis, obtaining a biopsy to further examine the histology can also be helpful. A Becker nevus should not have any nevus cells; rather, it will show increased numbers of melanosomes in both keratinocytes and melanocytes, greater number of hair follicles, increased melanophages at the upper dermis, and increased dermal smooth muscle.³There are variable amounts of acanthosis, papillomatosis, and hyperkeratosis.³

Because a Becker nevus is benign, no intervention or continued care of the nevus is required, unless the patient desires it for cosmetic reasons. Most Becker nevi are greater than 10 cm in diameter, which is too large for surgical removal. Many patients opt to simply remove the hair. For these patients, electrolysis or laser treatments can be used for hair removal. 


Other patients would also like to reduce or remove the pigment in the affected area. Treatment options for these patients include fractionated lasers or the Q-switched ruby laser, erbium:yttrium-aluminum-garnet (Er:YAG), or long-pulsed alexandrite laser. However, dermatologists are cautioned to warn their patients that laser treatments have shown promise but are not effective in all individuals and in many cases, a relapse may occur after treatment (especially with the use of fractionated lasers).^5-8

Our patient was determined to have a Becker nevus based on clinical appearance, especially the presence of hypertrichosis. This patient did not wish to have a confirmatory biopsy. He was advised that a Becker nevus does not require intervention, and he opted not to initiate any therapy. 


Shehni Nadeem, BA, is a medical student and Maura Holcomb, MD, is a dermatology resident at Baylor College of Medicine in Houston.


References 


1. Becker SW. Concurrent melanosis and hypertrichosis in a distribution 
of nevus unius lateris. Arch Derm Syphilol. 1949;60(2):155-160.
2. Person JR, Longcope C. Becker’s nevus: An androgen-mediated 
hyperplasia with increased androgen receptors. J Am Acad Dermatol. 1984;10(2 Pt 1):235-238.
3. Rapini RP, Bolognia JL, Jorizzo JL. Dermatology: 2-Volume Set. St. Louis, Mo.: Mosby; 2007:1715.
4. Dasegowda BS, Basavaraj G, Nischel, K, et al. Becker’s nevus syndrome. Indian J Dermatol. 2014:59(4):421. Available at ncbi.nlm.nih.gov/pmc/articles/PMC4103296
5. Kopera D, Hohenleutner U, Landthaler M. Quality-switched ruby laser treatment of solar lentigines and Becker’s nevus: A histopathological and immunohistochemical study. Dermatology. 1997;194(4):338-343.
6. Trelles MA, Allones I, Moreno-Arias GA, Vélez M. Becker’s 
naevus: A comparative study between erbium:YAG and Q-switched neodymium:YAG; clinical and histopathological findings. Br J Dermatol. 2005;152(2):308-313.
7. Choi JE, Kim JW, Seo SH, Son SW, Ahn HH, Kye YC. Treatment of Becker’s nevi with a long-pulse alexandrite laser. Dermatol Surg. 2009;35(7):1105-1108.
8. Meesters AA, Wind BS, Kroon MW, et al. Ablative fractional laser 
therapy as treatment for Becker nevus: A randomized controlled pilot study. J Am Acad Dermatol. 2011;65(6):1173-1179.

All electronic documents accessed on February 2, 2016.