Becker's melanosis: A report of 12 cases with atypical presentation

Authors

  • Abdullah Alfadley MD,

    Corresponding author
    1. From the Dermatology Division, Department of Medicine and Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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  • Bo Hainau MD,

    1. From the Dermatology Division, Department of Medicine and Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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  • Ahmed Al Robaee MD,

    1. From the Dermatology Division, Department of Medicine and Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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  • Nusrat Banka MD

    1. From the Dermatology Division, Department of Medicine and Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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Abdullah Alfadley, Head Section of Dermatology Department of Medicine (MBC-46) PO Box 3354 Riyadh 11211 Saudi Arabia E-mail: alfadley@kfshrc.edu.sa

Abstract

Becker's melanosis is a distinct clinical entity. It usually presents in adolescence as a unilateral, hyperpigmented, hairy cutaneous hamartoma. We report herein 12 cases of Becker's melanosis that differ in their presentation from classical Becker's melanosis, and we believe that such presentations are not uncommon.

Introduction

Becker's melanosis described by S. William Becker in 1949 as a localized hypermelanosis and hypertrichosis is a relatively common benign smooth muscle hamartoma.1 The characteristic presentation of Becker's nevus or Becker's melanosis is a circumscribed hyperpigmented patch with an irregular outline and associated hypertrichosis, developing usually in the second decade of life over the upper half of trunk and/or on the proximal upper extremities.2 Though this remains the commonest presentation, not all patients present with the classical features described by Becker. We describe 12 patients with an atypical presentation.

Case Reports

Twelve patients are summarized in Table 1.

Table 1.  Clinical data of patients 1–12 (see figures 1–3 and 5)
Pt no.SexAge of onsetLocationSizeColorHypertrichosisAcneAssociationsAtypical features
1MPubertyLeft flank20 × 15 cmBrown+EpilepsySite and size
2FBirthLeft flank15 × 20 cmBrownEarly age of onset. Site, size and no hypertrichosis
3MPubertyPubic area12 × 15 cmBrownCould not be assessedSite
4FPubertyMid and lower back20 × 30 cmDark BrownSite, size and no hypertrichosis
5MPubertyLeft upper leg 4 × 14 cmBrownSite and no hypertrichosis
6FPubertyLeft side of neck15 × 15 cmDark Brown+Site and no hypertrichosis
7FChildhood (1 year)Left deltoid12 × 12 cmBrown+Tiny keratotic follicular papules_Early age of onset
8MAdulthood (28 years)Left shoulder15 × 15 cmBrown+Tiny keratotic follicular papulesLate age of onset: 3rd decade
9FChildhood (3 years)Right arm, elbow and forearm30 × 15 cmBlack++EpilepsyEarly age of onset Site and size
10MBirthRight arm extending to elbow23 × 17.5 cmBrownish-black+Early age of onset and size
11MPubertyRight lower arm 8 × 10 cmBrownSite and no hypertrichosis
12MPubertyRight elbow and forearm10 × 15 cmBrown+_Site
Figure 1.

Patient no. 1. Hyperpigmented patch with hypertrichosis located on the left flank

Figure 2.

Patient no. 6. Hyperpigmented patch left side of neck with hypertrichosis

Figure 3.

Patient no. 10. Hyperpigmented patch with hypertrichosis over right arm, elbow and forearm

Figure 5.

Becker's melanosis of deltoids (a) with extensive hypertrichosis in the male, and (b) a brown patch with no hypertrichosis in the female

Histology

Four-mm skin biopsies were performed in the first 10 patients and all were reviewed on the same day. As seen in Table 2, basal hyperpigmentation, acanthosis and rete-ridge elongation was found in all patients. Clubbing of rete ridges was seen in eight out of 10 patients. Only patient no. 7 showed a minimal increase in smooth muscle in the dermis. Neither hyperplasia of the hair follicles, large sebaceous glands not thickening of the dermis were noted in any of our patients. Nevus cells were absent in all patients. There was no increase in the number of melanophages in the papillary dermis, as is noted in postinflammatory hyperpigmentation. Though there was increased basal cell pigmentation, elongation of the rete ridges does not support the diagnosis of a “café au lait” macule.

Table 2.  Histopathological findings of patients 1–10 (see figure 4)
Pt. no.AcanthosisRete ridges ElongationRete ridges ClubbingBasal PigmentationMelanocytesSmooth Muscle
1+ ++ + ++ + ++ + +NormalNormal
2+ + ++ + ++ + ++ + +NormalNormal
3+ ++ +0+IncreasedNormal
4+ ++ +0+ +NormalNormal
5+ ++ ++ ++ +IncreasedNormal
6+ ++ ++ ++ +NormalNormal
7+ ++ +++NormalIncreased
8+ ++ ++ + ++ + +IncreasedNormal
9++ ++ + ++ + +NormalNormal
10++ ++ + ++ + +NormalNormal
11Refused biopsy     
12Refused biopsy     
Figure 4.

Photomicrograph of patient no. 2 showing elongated rete ridges with clubbing and basal pigmentation. Hemotoxylin and eosin stain magnification ×40

Histopathological findings of patients no. 1 to 10.

Discussion

Becker's melanosis is rather a common skin lesion. The male to female ratio reported varies from 4 : 13 to 6 : 12. Higher incidence in males has been attributed to its androgen dependency. We agree with Happle et al. l that the true sex ratio may be 1 : 1 with an under reporting of lesions in females in whom the lesions may be inconspicuous because pigmentation is less intense and hypertrichosis may be mild or absent.3,6,10 In our patients male to female ratio was approximately 1 : 1.

The commonest age of presentation of Becker's melanosis is at puberty but congenital,4 familial,5 and late onset Becker’s6 are known to occur. Most of our patients had onset at puberty. Two patients had congenital Becker's melanosis. None had family history of a similar lesion. Clinically both Becker's melanosis and congenital smooth muscle hamartoma (CSMH) are characterized by hypertrichosis and hyperpigmentation; some authors have suggested that Becker's melanosis and CSMH are variants of the same hamartomatous process.7,8 In most cases of Becker's melanosis, however, the pigmentation and hypertrichosis are more prominent than in the smooth muscle component, whereas the reverse is true in CSMH. Becker's melanosis mainly consists of epidermal changes with only a minimal increase in smooth muscle, whereas CSMH is characterized by hyperplasia of smooth muscle bundles throughout the dermis.7,8 In both of our patients with congenital Becker's melanosis there was no smooth muscle hyperplasia. Only one of our patients (patient no. 7) showed an increase in smooth muscle on skin biopsy. The incidence of smooth muscle hamartoma in Becker's melanosis has not been determined, however, Becker's melanosis without smooth muscle hamartoma has been reported.9,14

Two of our patients had a rather early onset of lesions: one at age 3 years and the other at age 7 years. Late onset in the third decade of life was seen in one patient. Though onset during adolescence is common, wide variation in the age of onset can occur.

Becker's melanosis classically appears on the upper half of the trunk or proximal upper extremities.2 Other unusual sites have been described such as the face and lower limbs.3,9 Recently, Hsu et al. reported Becker's melanosis on the leg of a women without hypertrichosis.10 We describe patients having Becker's melanosis over unusual locations such as the neck, forearms, proximal lower limbs and lower half of the trunk, flanks and pubic area. Unusual locations appear to be common but such cases are either under reported or not recognized, especially when there is no associated hypertrichosis. Tymen et al. reported hypertrichosis in little more than 50% of patients with Becker's lesions.6 In our patients, five out of 12 lacked hypertrichosis.

Acneform eruptions confined to Becker's lesions were first reported by Burger and Ackerman in 1978.11 None of our patients had acneform eruptions, and we observed small keratotic follicular papules within the lesion in two of our patients. Onset in adolescence, presence of hypertrichosis and acneform eruption all suggest androgen-mediated hyperplasia.12

Becker's nevus syndrome is a phenotype characterized by the presence of Becker's nevus in association with unilateral hypoplasia of the breast or other cutaneous, muscular or skeletal defects.3,13 None of our patients had associated musculoskeletal defects, however, two patients had history of epilepsy.

We found only one report in the English literature reporting Becker's melanosis lacking hypertrichosis and a histology of smooth muscles hyperplasia.14 It is possible that such cases are not recognized as Becker's melanosis. Rower et al. reported five cases of progressive cribriform and zosteriform hyperpigmentation with onset during peripubertal or adolescent years.15 We agree with Hsu et al.,10 and Elder and Elenitsas16 that these reports are most likely cases of Becker's melanosis without hypertrichosis. The classical features described by Becker includes:

  • 1onset in the 2nd decade of life in adolescent or adult men;
  • 2appearing classically on the upper trunk or proximal upper extremities; and
  • 3with histologic changes comprised of increased melanin in basal cells and in the superficial dermis.

Though this remains the commonest presentation we believe that Becker's melanosis occurs:

  • 1with an equal incidence in both sexes;
  • 2anytime from birth to adulthood;
  • 3as a hyperpigmented patch with or without hypertrichosis;
  • 4anywhere over the trunk or extremities; and
  • 5with histological changes mainly confined to the epidermis with or without an increase in smooth muscle in the dermis.

We have presented these cases to emphasize that a high degree of clinical suspicion for Becker's melanosis is required when one encounters a hyperpigmented patch at an unusual location without associated hypertrichosis or smooth muscle hyperplasia on histology. Becker's melanosis is essentially a clinical diagnosis, however, a biopsy may be required in some patients to exclude other pigmentary disorders like nevocellular nevus, a large “café au lait” patch, congenital smooth muscle hamartoma and postinflammatory hyperpigmentation.

Acknowledgment

The authors would like to thank Ms. Alma B. Llaneta for typing this manuscript.

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