Tuesday, May 5

Becker's nevus - Becker melanosis

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What is Becker's nevus?

Becker's nevus (BN), also known as Becker's melanosis, is an unilateral, cutaneous hamartoma predominantly affecting males.
This form of pigmented nevoid melanosis was first described by American dermatologist, Samuel William Becker (1894–1964), in the year 1948. It is characterized by a large, hyperpigmented macule with irregular borders and late-set hypertrichosis.

The nevoid melanosis involved common sites are the trunk, arm, shoulder, chest, face, flank, buttock and leg. It tends to be more conspicuous in male patients, becoming apparent during adolescence. It appears to be androgen-dependent as it becomes more prominent after puberty and there is increased hairiness of the affected area. In some cases intralesional acne may develop. Researchers have also reported increased number of androgen receptors in the lesion when compared with unaffected skin.

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The frequency of Becker's pigmentary hamartoma is considered to be around 0.2% in the population. However, the prevalence can be much higher as the lesion may be less conspicuous in women and may go unnoticed and often get overlooked or misdiagnosed. These melanosis lesions are initially pale in color. They darken and become more conspicuous after sun-exposure. As the melanosis progresses, new macules develop beyond the margin of the initial patch and coalesce with it, giving a geographical contour. Fresh satellite macules may keep developing.

Becker's melanosis pathogenesis

The cause of Becker's pigmentary hamartoma is not fully understood. Though there are congenital cases, the lesion usually develops during childhood and early teenage years. Possibly a small patch of skin with the predisposition for these melanosis lesions may be present at birth. Male hormones contribute to its progression and its changes during puberty. The epidermis at the site shows mild acanthosis and hyperkeratosis with regular elongation of rete ridges.

Becker's melanosis complications

Malignant melanoma had been documented in patients with Becker's pigmentary hamartoma. Several cases of congenital BN have been reported. Book SE et al. reported a case of congenital Becker's pigmentary hamartoma with a familial association. A 16-month-old Child had a patch of melanosis on his right shoulder and upper pectoral area, extending down his arm. The patient's father also had a similar macule with hair on his left shoulder right from his childhood. The authors concluded that, "We believe this to be the first reported case of a congenital Becker's nevus with a familial association."
Becker melanosis - Becker's nevus
Becker melanosis - Becker's nevus
Sumit Kar et al. reported a 22-years-old male with coexistent Becker's nevus and type 1 neurofibromatosis. Neurofibromatosis type 1 is an autosomal dominant multisystem disorder, with cutaneous, neurologic and orthopedic manifestations. Mutation in neurofibromin gene located at chromosome 17q11.2 causes type 1 neurofibromatosis. It is a rare association of both the ailments in one individual.

George Issa et al. reported a case of giant BN and concurrent epidermal nevus (EN) in a 70 years old patient. He had a hyperpigmented scaly plaque extending along his left lateral thigh, knee and leg. "The biopsy of which demonstrates hyperkeratosis with acanthosis and increased pigmentation at the basal layer, consistent with an EN." There was also a lesion on the trunk which was diagnosed as Becker's pigmentary hamartoma.

Becker's Nevus Syndrome (BNS)

BNS is an association of nevoid melanosis with several unilateral developmental abnormalities of different organ systems such as breast hypoplasia, supernumerary nipples, aplasia of the pectoralis major muscle, mentally retardation, short stature, spina bifida, scoliosis, congenital adrenal hyperplasia, cardiac defects and an accessory scrotum.

Becker's melanosis treatment

The nevoid melanosis is generally asymptomatic and no treatment is usually necessary, except for cosmetic reasons. The hair on the melanosis patch can be removed by using epilation creams, shaving, waxing or threading. Small melanosis lesions may be surgically removed. Different laser systems have been used to treat hypertrichosis and hyperpigmentation with highly variable results. Standard acne treatments may control acne in the lesion.
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Reference:
1.Book SE, Glass AT, Laude TA. Congenital Becker's melanosis with a familial association. Pediatr Dermatol. 1997 Sep-Oct;14(5):373-5.
2.Kar S, Preetha K, Yadav N, Madke B, Gangane N. Becker's nevus with neurofibromatosis type 1. Ann Indian Acad Neurol. 2015 Jan-Mar;18(1):90-2.
3.Issa G, Blalock TW, Lesher JL. Patient with giant Becker's nevus and epidermal nevus. Dermatol Reports. 2011 Sep 12;3(2):e23.
Image source: http://en.wikipedia.org/wiki/File:Becker-Naevus.jpg
Image author: Siller
Image licence: cc-by-sa-3.0
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