Acquired Pigmentary Disorders

Abstract Skin pigmentation by melanocytes is regulated by complex mechanisms including melanoblast migration, melanosome transport, melanosome transfer and melanogenesis. Melanogenesis is influenced by UV light, and endocrine, paracrine and autocrine factors. This leads to a large differential diagnosis of pigmentary disorders. Additionally, melanocytes are highly immunogenic and can be targeted by the immune system, leading to vitiligo and halo naevi. Non‐melanin pigmentation arises from endogenous sources such as haemosiderosis, carotenoderma and ochronosis or exogenous pigmentation such as metals, mediation and tattoos.