Ultrastructural study of keratinocytes and melanocytes in vitiligo, progressive macular hypomelanosis and idiopathic guttate hypomelanosis

Background Keratinocytes regulate the proliferation, differentiation, and migration of melanocytes through production and release of a large array of cytokines, growth factors and mitogens. Objective The aim of this study was to assess the ultrastructural findings of melanocytes and keratinocytes in lesional and perilesional skin of vitiligo and compare these findings with two disorders of pigmentation: progressive macular hypomelanosis (PMH) and idiopathic guttate hypomelanosis (IGH). Patients and methods Skin biopsies were taken from lesional and apparently normal perilesional skin of 15 patients with vitiligo, PMH, and IGH (five patients for each disease). Smaller specimens (1 1 mm) were prepared to be examined by transmission electron microscopy. Results Transmission electron microscopy findings of vitiligo affected skin revealed absence of melanocytes and a distorted architecture of keratinocytes. Further, keratinocytes lacked melanosomes and had irregular nuclei and a prominent rough endoplasmic reticulum. In perilesional skin, the melanocytes showed a prominent rough endoplasmic reticulum and vacuolization and keratinocytes were of normal architecture but contained some vacuoles. In PMH, melanocytes were easily detected in lesional skin and they contained fewer and less electron-dense melanosomes than in perilesional skin. Keratinocytes were of normal architecture with few melanosomes that were less electron dense and solitary or clustered. In IGH, melanocytes were hardly detected and were of two types. One contained large, electron dense melanosomes, whereas the other contained melanosomes that were smaller, fewer and less electron dense compared with melanosomes of perilesional melanocytes. Keratinocytes and melanocytes in perilesional skin of both PMH and IGH were of normal architecture. Conclusion Structural keratinocyte changes, which are present in lesional and to a less extent in the apparently normal perilesional skin of vitiligo, may represent an active role of these cells in vitiligo. In contrast, keratinocytes were more or less normal in lesional and perilesional areas of PMH and IGH, which suggests that these two pigmentary disorders are primarily melanocytic in origin.