Most skin diseases occur in people of all nationalities, regardless of their skin color. Certain problems encountered in the skin are more common in people with different hues of skin, and sometimes a disorder seems more prominent because it affects skin color.
Variations in skin color
Skin color is determined by cells called melanocytes. Melanocytes are specialized cells within the skin that produce a pigment known as melanin. Melanin is produced and stored within special structures, known as melanosomes, contained in the melanocytes.
The melanocytes make up only a small percentage of overall skin cells. In fact, only two to three percent of all skin cells are melanocytes. The variation in skin color we see across all people is determined by the type and
amount of melanin produced by the melanocytes.
All people essentially have the same number of melanocytes. A recent theory indicates that the differences in skin color are really a reflection of the skin’s ability to protect against ultraviolet radiation. Persons living closer to the equator produce more melanin because the ultraviolet radiation is more intense, and groups of people living further away from the equator produce less melanin, resulting in lighter skin color.
One reason treating pigmented skin can be somewhat difficult is that traditionally textbooks have only had black and white photographs. Additionally, many lesions have been described as red, pink, salmon, or fawn-colored.
This certainly is true in Caucasian skin; indeed many of the textbooks that were written had this as the majority patient type. However, in tan, brown, or dark-brown skin, inflammation can look grey, copper, or violaceous in color. Additionally, certain conditions will have a slightly different presentation in pigmented skin (see pityriasis rosea).
Post-inflammatory hyperpigmentation and hypopigmentation
Melanocytes are very sensitive cells and can either stop producing color or produce excessive color in cases of inflammation. Normally, in children, the cells stop producing color (I explain to parents that the cells tend to go to sleep), especially in irritation of the diaper area.
It is very common in a child to have a very light area of post-inflammatory hypopigmentation. This is where the inflammation of diaper irritation causes the melanocytes to stop producing color, leaving light or white patches. With the appropriate treatment, the color almost always returns to normal within a few weeks.
In older patients, inflammation can lead to post-inflammatory hyperpigmentation. This is most commonly seen in areas where acne blemishes heal, leaving a dark spot behind. These too will fade with time; however, it can be quite persistent.
Vitiligo is a skin condition that occurs in all people, but it is most noticeable in patients with tan, brown, or dark brown skin. I believe that vitiligo is really the end stage of several different disorders.
In some disorders, the melanocytes are attacked by the immune system and they die. In other conditions, the melanocytes are preprogrammed to die early. No matter what the cause, ultimately, patches of vitiligo are white patches devoid of melanin. Because these areas lack natural protections, vitiliginous patients must wear sunscreens to prevent ultraviolet radiation exposure and subsequent cancer later in life.
In the majority of cases, vitiligo is probably the result of an auto-immune or inflammatory attack on melanocytes. In these cases, topical anti-inflammatories and phototherapy, most notably narrow-band ultraviolet B, tend to be most effective. We have a success rate of approximately 75 percent in our clinic. In the remaining cases, these are probably related to a genetic program in the melanocytes where they die prematurely. Usually with the appropriate treatment, signs of vitiligo can be reversed in one to two months.
Pityriasis alba is a condition where white patches occur on the arms, trunk and, most notably, on the face. This is an extremely common condition seen primarily in adolescent patients of color. It is a result of a very mild irritation and/or eczema leading to post-inflammatory hypopigmentation where the melanocytes temporarily stop producing color.
Mild topical anti-inflammatory lotions, gentle cleansing bars, and ultra moisturizing lotions can be used to treat pityriasis alba. The loss of color in this condition is usually only temporary and is most notably seen on the cheeks of adolescents.
Next week: more skin problems common to people of color
Charles E. Crutchfield III, MD is a board certified dermatologist and Clinical Professor of Dermatology at the University of Minnesota Medical School. He also has a private practice in Eagan, MN. He has been selected as one of the top 10 dermatologists in the U.S. by Black Enterprise magazine and one of the top 21 African American physicians in the U.S. by the Atlanta Post. Dr. Crutchfield is an active member of the Minnesota Association of Black Physicians, MABP.org.