Pigmentation Disorders: Hyperpigmentation and Hypopigmentation

Disorders of pigmentation can occur as congenital or acquired diseases and are classified as hyperpigmentation or hypopigmentation. Hyperpigmentation is the result of an increase in melanin production, distribution, or transport. Common hyperpigmentation disorders include melasma, ephelides (freckles), solar lentigines, and postinflammatory hyperpigmentation. Hypopigmentation can result from a reduction in the number of melanocytes, an inability of the melanocytes to produce melanin or impaired transfer of melanosomes to keratinocytes. Hypopigmentation disorders include vitiligo, pityriasis alba, and postinflammatory hypopigmentation. Non-melanic pigmentary disorders are caused by the deposition in the dermis of endogenous or exogenous pigments.