They are not diagnostic of a specific disease, but may contain significant diagnostic clues. In inflammatory lesions of the epidermis, leukocytes will often migrate into the epidermis, and process called exocytosis. The primary pigment present in the skin is melanin, produced by melanocytes of the stratum basale of the epidermis and hair follicles and perivascularly in the dermis. Changes involving melanin pigment in the skin are hyperpigmentation, hypopigmentation and pigmentary incontinence. Hyperpigmentation Increased pigmentation of the skin can result from increases in numbers of melanosomes, melanosome size, maturation of melanosomes, or increases in numbers of melanocytes.
Hyperpigmentation is very chronic in chronic inflammatory skin disease and endocrine dermatoses.
Hypopigmentation Decreased skin pigmentation can be congenital or hereditary, or acquired. The congenital or hereditary forms develop due to lack of pigment production, or lack of transfer to epidermal cells. This depigmenting change occurs secondary to damage to the basal epithelium or basement membrane, with accumulation of the pigment in macrophages and free in the superficial dermis.