Symmetrical bilateral Becker melanosis: A rare presentation
- Author(s): Grim, Kelli D;
- Wasko, Carina A
- et al.
Published Web Locationhttps://doi.org/10.5070/D30t98s3gz
Symmetrical bilateral Becker melanosis: A rare presentationDepartment of Dermatology, Baylor College of Medicine, Houston, Texas. firstname.lastname@example.org
Kelli D Grim MD, Carina A Wasko MD
Dermatology Online Journal 15 (12): 1
Becker melanosis, also known as Becker nevus, is a relatively common cutaneous hamartoma. The condition is classically characterized by a unilateral, hyperpigmented patch with varying degrees of hypertrichosis on a peripubertal individual. As Becker nevi are generally singular in a given individual, there are very few reported cases of multiple or bilateral lesions. We herein report a rare case of bilateral, symmetrical, non-syndromic Becker melanosis and we discuss possible pathogenesis and current treatment options.
Becker melanosis, or Becker nevus, was first described by Becker in 1949 as a "concurrent melanosis and hypertrichosis in the distribution of nevus unius lateris."  Becker melanosis has since been characterized by unilateral, hyperpigmented macules and patches located on the proximal upper extremities, with or without hypertrichosis. Becker melanosis is thought to be an androgen-dependent lesion with increased androgen sensitivity and receptor density within the lesion [2-6]. There are very few reports in the literature of multiple Becker nevi in the same individual [7-12]. We present a rare case of bilateral, symmetrical Becker melanosis.
|Figure 1. Bilateral, symmetrical, hyperpigmented macules and patches in an archipelago configuration extending across the anterior chest. Sparse hair was noted throughout.|
A 45-year-old healthy African-American man presented with hyperpigmented, bilateral lesions of the anterior chest. According to the patient, the asymptomatic lesions first appeared during adolescence and continued to darken over time. He denied any history of trauma, excessive sun exposure, or preceding inflammation in the area.
Physical examination showed bilateral, symmetrical, hyperpigmented macules and patches in an archipelago configuration extending across the anterior chest (Fig. 1). Sparse hair was noted throughout. Based on the patient's history and physical exam, a clinical diagnosis of Becker melanosis was made.
Becker melanosis is a relatively common cutaneous hamartoma with a variety of clinical presentations. The condition has been described as single or multiple, unilateral or bilateral, acquired or congenital, hypertrichotic or hairless, and syndromic or non-syndromic [1, 6, 13, 14, 15]. In a study by Tymen et al., the hamartoma occurred with a frequency of 0.52 percent in a sample of 19,302 male French military recruits between the ages of 17 and 26 . Fifty percent of the recruits reported the age of onset at less than 10 years of age and 50 percent between 10 to 20 years of age . Hypertrichosis was estimated to occur in 50 percent .
The male to female ratio of Becker melanosis has been approximated to be between 4:1 and 6:1 [15, 17, 18]. The frequency in females is less established, possibly due to the androgenic pathogenesis of the lesion. Becker melanosis in women is less conspicuous with comparatively less hypertrichosis and hyperpigmentation than lesions in men, presumably due to relatively less circulating androgens [15, 17] Subtle presentations could lead to underreporting and the true ratio may actually be closer to 1:1 [15, 17, 19].
Becker nevus syndrome, defined as Becker melanosis with concurrent developmental defects, reportedly has a male to female ratio between 1:1.5  and 1:2 . The apparent female predominance may be due to increased reporting in women since ipsilateral breast and/or areolar hypoplasia would be more conspicuous in females than in males [6, 15]. It is possible that the true sex ratio of Becker nevus syndrome is also near 1:1 .
Becker melanosis is an androgen-dependent lesion with a disturbance in androgen receptor activity [2-6]. Increased androgen receptor density in Becker melanosis has been found via immunohistochemical staining [2, 3], reverse transcriptase polymerase chain reaction (RT-PCR) of androgen receptor messenger RNA (mRNA) , and ligand-binding assays [5, 6, 21]. In addition, the characteristic hypertrichosis and hyperpigmentation of Becker melanosis is similar to genital skin [2, 3]. Acneiform eruptions , superimposed tinea versicolor infection possibly due to increased sebum production [6, 22, 23], and association of Becker melanosis with an accessory scrotum provide further credence to the androgen-mediated theory [6, 19, 21, 24]. Androgenic sensitivity could also explain the peripubertal manifestation of classic Becker melanosis as well as the association with hypoplasia of the breast and areola in both males and females as this could antagonize estrogenic effects on breast development .
Whether Becker nevus and Becker nevus syndrome occur sporadically is uncertain. Autosomal dominant inheritance with incomplete penetrance and variable expressivity has been hypothesized . Other authors have espoused that paradominant inheritance would better explain the regional predilection and mosaic pattern of Becker nevus [6, 15].
Histological inspection of Becker melanosis shows epidermal acanthosis, elongation and fusion of adjacent rete ridges, variable hyperkeratosis, and basal layer hyperpigmentation [3, 6, 19]. Dermal smooth muscle hyperplasia is another recurrent feature of Becker melanosis, leading some to believe that Becker nevus is a continuum of hamartomatous processes along with congenital smooth muscle hamartoma (CSMH) . However, Becker melanosis without smooth muscle hyperplasia has been reported in the literature [17, 19].
Several reports of multiple Becker nevi exist in the literature (Table 1). Ferreira et al. reported a congenital case of a 4-year-old girl with roughly symmetrical, bilateral, well-defined Becker nevi extending over her scapular regions, shoulders, and arms . Khaitan et al. presented a case of a 28-year-old male with 7 distinct lesions with unilateral presentation and sharp, midline cut-off that had developed during puberty . De la Torre et al. reported a case of systematized, bilateral Becker nevus syndrome with associated hypoplasia of the left areola [6, 9]. Bansal et al. reported a case of non-symmetrical, bilateral Becker nevi in an 18-year-old male that had developed peripubertally . Khatami et al. discussed a 14-year-old male with widespread Becker nevi on the anterior chest, upper abdomen, upper arms, and bilateral scapular region, first noticed at the age of 8 years old; the lesions noted on the posterior trunk were roughly symmetrical . To the authors' knowledge, there have been only two cases of bilateral Becker melanosis described as roughly symmetrical in the English language literature, both cases being reported in the pediatric population [7, 12]. Our case represents an acquired, symmetrical, non-syndromic bilateral Becker nevus, a rare presentation.
Often the cosmetic appearance is the most alarming feature of Becker melanosis, as in the case of our patient. Therapeutic modalities are currently limited. Laser therapy options include non-specific, ablative lasers, such as the 2940-nm erbium:yttrium-aluminum-garnet (Er:YAG) laser, and pigment-specific, Q-switched lasers, such as alexandrite, ruby and neodymium:YAG (Nd:YAG) [26, 27]. One study found that one-pass Er:YAG treatment was superior to three, consecutive, Nd:YAG treatment sessions . Fractional resurfacing has also been utilized in two reported cases with notable lightening of lesions . Patients with the diagnosis of Becker nevus should undergo evaluation for associated soft tissue, muscular and skeletal developmental abnormalities . Patients found to have isolated Becker nevus can be reassured about the benign nature of this condition.
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