Acquired Pigmentary Disorders

Abstract Abnormal skin pigmentation represents a common skin problem which may be congenitally determined or acquired during life. The former are discussed in Chapter [70]. Acquired pigmentary disorders encompass a broad range of diseases resulting not only in abnormal melanin pigmentation of the skin but also in skin colour change produced by a variety of other endogenous and exogenous pigments. The first part of this chapter examines the melanocyte and normal melanogenesis. The second part discusses not only acquired abnormalities of skin pigmentation resulting from disturbances in melanin pigmentation but also those disorders due to other endogenous or exogenous pigments. The third part describes acquired hypomelanosis including disorders with reduced pigmentation (hypopigmentation) and total absence of pigmentation (depigmentation). In the final part, non‐melanin pigmentation of the skin is examined.