HYPO-AND HYPERPIGMENTATION OF THE SKIN' A REVIEW* By Sr)N¾ G. lvI.D. Mount Fernon, N.Y. THE STUDY OF pigmentation of the skin is important to both the physician and the layman. To the physician, aberrations of skin color are diagnostic aids in detecting illness. To the therapeutist falls the problem of alleviation of cosmetic defects. To the biochemist and physiologist studies are becoming more enlightening in the relationship of enzymatic sys- tems to endocrine function. Sociologically, skin pigmentation encompasses a scope as diminutive as the cosmetic appearance of an individual to the vastness of an entire race of people. Skin pigmentation consists of the following basic colors: red, blue, yellow, and brown white, of course, being the absence of color. Red is derived from the oxyhemoglobin within the blood vessels of the skin, blue from the reduced hemoglobin and venules, yellow from the carotene, and brown from the melanin. To understand the relationship of these prod- ucts to color, a description of the histology of normal skin is important. The skin consists of the epidermis and dermis. The epidermis has five layers--from without inward: the stratum comeurn consisting of dead or dying cells the stratum lucidurn which is normally a poorly defined layer of clear acidophilic cells the thin stratum granulosum, rich in dark gran- ules of keratohyaline the stratum malpighii having the greatest number of cell layers and the stratum germinativum or basal cell layer consisting of basal cells, clear cells, and dendritic cells (1, 2). The pigment of the epidermis is produced from cells in and immediately about the basal cell layer. According to various authorities all three types of cells in the basal cell layer under proper stimulation are capable of pro- ducing melanin. Other cells known as chromatopores merely phagocytize melanin and appear pigmented. These chromatophores lie in the upper corium. The evaginations of the dermis into the epidermis are known as papillae and are rich in terminal capillary loops which connect with a sub- papillary plexus of blood vessels. Here is the source of red and blue color (2). * Presented at the May 15, 1953, Meeting, New York City. 245

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Skin rarely. shows a red coloration except under inflammation because of the screening out effect of the epidermis and especially. the melanin content. In the dark-skinned negro, ery'thema is di•cult to detect due to the heavy melanin screen. Also the venous part of the subepidermal plexus of blood vessels, with the reduced hemoglobin being carried away from the skin, provides a toning down due to its blue coloring. Blue is especially seen in cases of cy'anosis where little oxy'hemoglobin is actually present. Carotene which adds a strong yellow component to normal skin is pres- ent not only in the subcutaneous fat but also in the stratum comeurn. Due to its lipin content, the corneal lay.er has an a•nity' for carotene and stores it. Carotene, which is a precursor of Vitamin A, is normally in- gested in foods. Anatomically it thus becomes clear why. the palms and soles which have thicker strata cornea are comparatively. yellowet, why eyelids and skin on the flexural surface of the forearms with a thin epidermis reveal the blue of the blood vessels, why areas with increased granular layers block out with opaqueness deeper cellular elements and appear white. These substances are present in all normal skins with variations in amount and location. The most important pigment is melanin and it is of worth to describe its production and physiologic relationship at this time. It is now popularly. believed that the melanin producing cell is in the epidermal basal cell layer and is called the melanocyte. In this cell is an enzyme called tyrosinase which in the presence of molecular oxygen "catalyzes the oxidation of the colorless amino acid, tyrosine, to melanin, an insoluble polymer of high molecular weight." It has been shown that this biochemical reaction takes place when the skin is radiated with radiant energy. (ultraviolet light etc.). Copper plays an essential role in melanization by attaching to active centers on apotyrosinase. Present in the epidermis are sulfhydryl groups which normally inhibit the copper required for tyrosinase activity, and help to maintain a balanced melanin production. Disturbances in this chemical equation are responsible in part for abnormal melanin pig- mentation (3). Physiologically the metabolism of melanin is influenced by endocrine stimulation from the adrenals, pituitary, thyroid, and gonads. Disturb- ances in glandular activity result in pigmentary disturbances. The activity of Vitamin A, C, and parts of the B complex is also important. In normal instances, melanin is produced in the basal cell lay.er of the epidermis. The actual cells involved and their origin has been a matter of scientific dispute for many. years. The dendritic cells and the clear cells in the epidermis rather than the basal cells themselves have been accredited with pigment formation. However, the origin of these cells was disputed until recently.. The school of Bruno Bloch and older authors considered that the dendritic cells were products of pigment-producing ectodermal