Linear chains of amino acids that singly or in multiples of two or more form into proteins. Chains of just two amino acids are called, chains of three are, and any more are polypeptides.inear chains of amino acids that singly or in multiples of two or more form into proteins. Chains of just two amino acids are called, chains of three are, and any more are polypeptides.
Vitiligo: A Common Cause of Loss of Skin Pigment. Melanin is the pigment that gives the skin its characteristic color. Vitiligo is caused by a loss of pigment in the skin, due to destruction of pigment-forming cells known as melanocytes. Although vitiligo affects all races equally, it is more noticeable in dark-skinned people. Vitiligo can cause cosmetic problems.
Sometimes the hair in these areas also turns white. It happens when the skin's pigment-producing cells called melanocytes die. White patches can appear anywhere on the body (generalized vitiligo) or just in one area (focal vitiligo). Researchers suspect that vitiligo is one of many autoimmune diseases.he exact cause of vitiligo is unknown at this time; however, scientists have several different theories. One theory suggests that vitiligo is an autoimmune disease in which the body destroys melanocytes for no known reason.