Disorders of hyperpigmentation

Chapter 1 reviewed the biology of human skin pigmentation, and it is now appropriate to consider the pathology of the melanin pigmentary system and, if possible, to clarify the mechanisms producing these abnormalities. Basically, disturbances in human pigmentation manifest clinically as either excessive pigmentation (hyperpigmentation) or deficient pigmentation (hypopigmentation). Any respectable textbook of dermatology will provide lists of the legion conditions which fall under the rubric of the hyperpigmentation and hypopigmentation disorders respectively. Most of these are rare and of no interest to the general reader. This chapter will discuss some selected examples of the hyperpigmentation disorders and the following chapter will consider certain conditions associated with hypopigmentation.