To the Editors:
We read with interest the report by Torres-Álvarez et al1 about the damage of basement membrane (BM) in melasma, in which the authors suggest that “the damage to BM may facilitate the fall or the migration of active melanocytes and the melanin into the dermis was reflected in the constant hyperpigmentation of melasma.” Melasma has broad racial and personal differences, and the lesion's state varies even in one individual person.1,2 A fractional laser has been a popular modality in the treatment of melasma.2,3 However, partial aggravation by this laser treatment is not avoidable in some lesions of the melasma in Asian patients.4 After reading this report, we thought that the possibility of migrating melanocytes with disrupted BM is associated with an aggravation of melasma after a fractional laser, which is sometimes encountered in the melasma patients of Asian skin. BM damage is shown in this report1 as a decrease of collagen IV. The integrity of a BM complex is composed of collagen IV, laminin, and collagen VII, processed extracellular matrix, etc. Recently, it has been found that the extracellular domain of syndecan-2 (SDC-2) as cell surface receptor was associated with soluble and/or insoluble factors in the extracellular matrix.5 Some of us previously demonstrated that SDC-2 was associated with melanin synthesis and migration of melanocytes.5 SDC-2 was not expressed in normal BM. We observed the expression of SDC-2 in the lesional melasma of 2 Korean women before and after the fractional laser. Expression of SDC-2 and amount of melanin pigment were assessed by immunohistochemistry and Fontana-Masson staining, respectively.
In patient 1, who showed clinical improvement, Fontana-Masson staining of lesional melasma showed decrease of melanosomes while SDC-2 was decreased along the BM area (Fig. 1). In Fontana-Masson–stained melasma sections, the amount of melanin was significantly increased in all epidermal layers and free melanin and dermal melanophages were seen in lesional skin before the treatment (Fig. 1A). In patient 2, who showed clinical aggravation of melasma lesion, Fontana-Masson staining of lesional melasma showed increase of melanosomes while SDC-2 was increased along the BM area (Figs. 2, 3). Moreover, in lesional skin, we detected a protrusion of pigmented cells into the dermis. In 2 paired nonlesional skin samples, no evidence of damage was shown in BM.
Recently, a few studies have explained the finding of pendulous epidermal melanocytes with immunohistochemistry.1 In the present study, the protrusion of melanocyte was not improved in our patients but rather aggravated after the fractional laser treatment. Unexpectedly, with Fontana-Masson stain, we observed damage on the basal membrane in melasma lesions; this damage was observed as total absence of BM and partial disruption along the BM. In this study, preceding BM disruption and hyperactive melanocytes may have an aggravating role after fractional laser because this laser can make further BM damage.1
Taken together, it seems that a laser, which can make further BM damage, may make melanocytes hyperactive and migratory. The abnormality of the BM could be produced through an increase in the activity of matrix metalloproteinases, causing the degradation of type IV collagen and type VII collagen1 or replacement by abnormal deposition of extracellular matrix, such as SDC-2. Therefore, gentle treatment not to affect BM is mandatory to get satisfactory and safe outcome in the treatment of melasma.
1. Torres-Álvarez B, Mesa-Garza IG, Castanedo-Cázares JP, et al.. Histochemical and immunohistochemical study in melasma: evidence of damage in the basal membrane. Am J Dermatopathol. 2011;33:291–295.
2. Katz TM, Glaich AS, Goldberg LH, et al.. Treatment of melasma using fractional photothermolysis: a report of eight cases with long-term follow-up. Dermatol Surg. 2010;36:1273–1280.
3. Rokhsar CK, Fitzpatrick RE. The treatment of melasma with fractional photothermolysis: a pilot study. Dermatol Surg. 2005;31:1645–1650.
4. Lee HS, Won CH, Lee DH, et al.. Treatment of melasma in Asian skin using a fractional 1,550-nm laser: an open clinical study. Dermatol Surg. 2009;35:1499–1504.
5. Choi Y, Chung H, Jung H, et al.. Syndecans as cell surface receptors: unique structure equates with functional diversity. Matrix Biol. 2011;30:93–99.