Synonyms: Becker melanosis, pigmented hairy naevus of Becker

Becker's naevus is a form of epidermal naevus (birthmark). It usually appears around puberty as a hyperpigmented patch, most often found on the upper trunk or shoulders.^1,2,3

Aetiology¹

There is overgrowth of the epidermis (upper layers of the skin), pigment cells (melanocytes) and hair follicles. It may be due to a gene defect (as yet unidentified), perhaps triggered by circulating androgens, which would explain its onset during adolescence.

Epidemiology

• It is more common in men.
• One study reported a prevalence of 0.52% in men aged 17-26 years.⁴

Presentation^1,2

• A large brown area, sometimes covering half the upper back or chest. Most lesions become hairy (hypertrichosis).
• After puberty it often becomes darker and expands, usually over a period of 1-2 years.
• Occasionally acne may develop in the naevus.
• Some fading (reduced pigmentation) may occur in adulthood.
• One case of bilateral, symmetrical pigmentation is reported - this is unusual.³

Diagnosis

The age of onset, site and the fixed nature of the lesion are usually enough to make the diagnosis.

Differential diagnosis⁵

• McCune-Albright syndrome (with café-au-lait patches on the skin).
• Pityriasis versicolor is usually symmetrical and slightly scaly.

Histology^3,6

• Epidermis: acanthosis and hyperpigmentation of the basal layer, with elongation and fusion of adjacent rete ridges and variable hyperkeratosis.
• Dermis: hyperplasia of the dermal smooth muscle and melanophages.

Management¹

• No treatment is necessary except for cosmetic reasons; usually reassurance and a diagnosis are enough.
• For cosmetic treatment of the lesion:
  • Electrolysis or laser treatment may help with hair removal.
  • Laser treatment can sometimes reduce the pigmentation, but may be ineffective or may worsen the lesion.
  • Fractional resurfacing has also been used to lighten the lesions.³
• For acne in the lesion, use standard acne treatments.
• If there is doubt about the diagnosis (e.g. possible melanoma), urgent referral is appropriate.

Prognosis

The naevus remains indefinitely.²

Becker naevus syndrome^1,6,7

This is a Becker's naevus with additional abnormalities of underlying tissues derived from ectoderm. It is a type of epidermal naevus syndrome. There may be underdevelopment or overdevelopment of underlying structures, including:

• Smooth muscle hamartoma.
• Hypoplasia of breast.
• Spina bifida or scoliosis, pectus carinatum, pectus excavatum.
• Adrenal hyperplasia.
• Asymmetry of limbs, trunk or face.
• Umbilical hernia.
• Supernumerary nipple, accessory scrotum.

History

It is named after S. William Becker who first described the lesion in 1949. Becker naevus syndrome was described in 1995 by Happle.

Document references

1. Becker naevus; New Zealand Dermatological Society (DermNet NZ) September 2010
2. Becker's Naevus, Dermatology Information System
3. Grim KD, Wasko CA; Symmetrical bilateral Becker melanosis: A rare presentation. Dermatol Online J. 2009 Dec 15;15(12):1. [abstract]
4. Tymen R, Forestier JF, Boutet B, et al; (Late Becker's nevus. One hundred cases (author's transl)). Ann Dermatol Venereol. 1981;108(1):41-6. [abstract]
5. Rivers JK et al; Becker Melanosis, Medscape, Apr 2010
6. Cosendey FE, Martinez NS, Bernhard GA, et al; Becker nevus syndrome. An Bras Dermatol. 2010 Jun;85(3):379-84. [abstract]
7. Steiner D, Silva FA, Pessanha AC, et al; Do you know this syndrome? An Bras Dermatol. 2011 Feb;86(1):165-166. [abstract]

Acknowledgements