The Role of Macrophages in Pigmentary Disorders

Diseases associated with skin pigmentation include hyperpigmentation and hypopigmentation. Macrophages are involved in melanogenesis and the development of skin pigmentary disorders, and they affect the production and distribution of melanin mainly through phagocytosis and secretion. They can either phagocytose melanin and deposit it in the dermis or secrete a variety of cytokines like interferon (IFN)-γ, tumor necrosis factor (TNF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and some interleukins (ILs) such as IL-1, IL-6, IL-8, and IL-18. The interaction between macrophages and other cells is responsible for the secretion of these cytokines. Macrophages can also promote pigmentation in hyperpigmentation disorders, such as post-inflammatory hyperpigmentation (PIH), drug-induced pigmentation (DIP), senile lentigo (SL), and melasma, as well as hypopigmentation disorders such as vitiligo and halo nevus (HN). In this review, we summarize the role of macrophages in the development of pigmentary diseases and provide new insights for the identification of potential targets for pigmentary diseases.