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Hyperpigmented patch on the back

A family physician noted an asymptomatic patch on the back of his 24-year-old patient during her annual physical. The patient reported that it was not present during childhood, and to her best recollection, it appeared around the age of 15 and had remained unchanged since then.

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Hyperpigmented patch on back

Large unilateral hyperpigmented patches on the trunk with onset around puberty are the hallmark of a Becker nevus, also more descriptively called pigmented hairy epidermal nevus.

Becker nevi are a form of epidermal nevus that usually occur on the upper back or chest. They most commonly develop during puberty when there are increasing circulating levels of androgens. (Becker nevus cells are androgen sensitive.) This is consistent with this patient’s history of the lesion developing in her teens when the lesions become hyperpigmented and noticeable. The localized androgen sensitivity also can lead to unilateral hypoplastic breast growth when it occurs on the chest in young women.

The lesions are more common in males than females and often have associated hypertrichosis. The etiology is not certain but is thought to be due to regional loss of heterozygosity during embryogenesis leading to the abnormally elevated levels of androgen receptors and increased androgen sensitivity in the basal keratinocytes and dermal fibroblasts.

Laser is the most effective therapy for the hyperpigmentation and for hypertrichosis when present. If a young woman with a Becker nevus has breast hypoplasia, spironolactone (an antiandrogen) has been helpful in restoring breast growth. For this patient, the hyperpigmented patch was asymptomatic and not troublesome, so she opted not to treat it.

Photo and text courtesy of Daniel Stulberg, MD, FAAFP, Department of Family and Community Medicine, University of New Mexico School of Medicine, Albuquerque.

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