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American Journal of Dermatopathology:
doi: 10.1097/DAD.0b013e31822e6812
Letters to the Editor

Acquired Dermal Melanocytosis of the Back in a Caucasian Woman

Fauconneau, Antoine*; Beylot-Barry, Marie M.D, PhD, PU-PH*; Vergier, Béatrice M.D, PhD, PU-PH; Robert-Barraud, Claire M.D, PhD; Doutre, Marie-Sylvie M.D, PhD, PU-PH*

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*Service de Dermatologie, Hôpital Haut-Lévêque, CHU Bordeaux, Avenue de Magellan, Pessac, France

Service d'Anatomie et Cytologie Pathologique, Hôpital Haut-Lévêque, CHU Bordeaux, Avenue de Magellan, Pessac, France

Private practice, 4 Cours Tourny, Périgueux, France

The authors have no funding or conflicts of interest to declare.

To the Editor:

Dermal melanocytoses are a broad group of affections in which scattered dendritic or spindle-shaped melanocytes are present in the dermis and result in a blue-greyish pigmentation. We report the case of an acquired dermal melanocytosis (ADM) on the back of an adult white woman.

A 34-year-old woman presented with a blue-greyish hyperpigmentation of the upper back that appeared when she was a teenager (Fig. 1). It was not symptomatic. The patient did not report any infection or medicine-taking at the time the lesion arose. The clinical examination was otherwise normal. Histopathological examination of a punch biopsy showed a normal epidermis and scattered mature melanocytes in the dermis close to elastic fibers and collagen bundles (Figs. 2A, B). Immunostaining with A103/melanA antibody confirmed these cells were melanocytes (Fig. 2C). These findings were consistent with the diagnosis of ADM. The location was unusual and did not meet criteria for any previously described form.

Figure 1
Figure 1
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Figure 2
Figure 2
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The group of dermal melanocytoses comprises congenital and acquired forms. Several entities are described regarding location, age of onset, and clinical course. Although Mongolian spot is located in the lumbosacral area and regresses during childhood, Ito's naevus is typically located on the shoulder, neck, and scapular region, and Ota's naevus is located on the face.1,2 Acquired forms are rare and occur mostly in Asian woman, usually on the face. They include acquired bilateral naevus of Ota-like macules (Hori naevus) and acquired unilateral Ota naevus (Sun naevus). Extrafacial ADM are even rarer and have been reported on the back, limbs, or extremities.3 They appear in childhood or early adulthood and only rarely in older adults. These lesions are benign, and very few cases of malignant evolution have been described.

Their pathophysiology remains poorly understood. It is widely thought that melanocytes locate in the dermis as a result of an aborted migration during the embryonic period.1,2,4 It is less likely that melanocytes come from the basal layer of the epidermis “dropping off”.4 Interaction with collagen bundles and elastic fibers seems fundamental in the pathogenesis. Ultrastructural studies have indeed evidenced an extracellular sheath around melanocytes in Mongolian spot that shrinks as the lesion disappears. On the other hand, the persistence of this sheath in other lesions might explain why they are permanent.2

The existence of acquired lesions is more intriguing. Immature “dormant” melanocytes could be present in the dermis from birth and activate later in life.2,4 Mizushima et al5 found such “dormant melanocytes” in the perilesional skin of a patient with ADM. It is still unknown which signal activates the melanin-producing pathway of these cells, although UV rays, hormonal factors, and trauma have been incriminated.5 Interaction with collagen and elastic fibers could also be involved.2 Last, the clear predominance of ADM in Asian women and familial cases suggests the role of genetic factors.

Treatment is elusive given the depth and the extent of the lesions, although laser treatment provides good results.4 Combined protocols aimed at preventing posttherapeutic hyperpigmentation include laser and topical bleaching treatment.4

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REFERENCES

1. Mizoguchi M, Murakami F, Ito M, et al.. Clinical, pathological, and etiologic aspects of acquired dermal melanocytosis. Pigment Cell Res. 1997; 10:176–183.

2. Roth B, Grezard P, Balme B, et al.. Mélanocytose dermique acquise: étude anatomo-clinique et ultrastructurale. Ann Dermatol Venereol. 2002; 129:409–412.

3. Harrison-Balestra C, Gugic D, Vincek V. Clinically distinct form of acquired dermal melanocytosis with review of published work. J Dermatol. 2007; 34:178–182.

4. Park JM, Tsao H, Tsao S. Acquired bilateral nevus of Ota-like macules (Hori nevus): Etiologic and therapeutic considerations. J Am Acad Dermatol. 2009; 61:88–93.

5. Mizushima J, Nogita T, Higaki Y, et al.. Dormant melanocytes in the dermis: do dermal melanocytes of acquired dermal melanocytosis exist from birth? Br J Dermatol. 1998; 139:349–350.

© 2012 Lippincott Williams & Wilkins, Inc.

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