Skin can also be yellowed by liver disease—a condition called jaundice. The pigment bilirubin (which is yellow) is not able to be processed by the liver so that there is an accumulation of the molecule in all areas of the body; it is most noticeable in the whites of the eyes and in the skin. Other color-related skin conditions include skin darkening from tumors of the pituitary gland, which makes melanocyte-stimulating hormone (MSH) that darkens the skin. Patients with Addison’s disease have an excess of ACTH (adrenocorticotropic hormone) that mimics MSH and causes activation of the melanocytes. A lack of oxygen can be reflected in the skin. Initially, the skin will whiten from a lack of oxygenated hemoglobin, which is the red-pigmented molecule that gives skin its coloration. If this condition becomes prolonged, the skin will develop cyanosis—a bluish discoloration, from an excess of darker red-colored deoxygenated hemoglobin. Some babies will be born with heart defects that cause mixing of oxygenated and deoxygenated blood, so they will be born with cyanosis.
SKIN CANCER Skin cancer, like other cancers, occurs when cells of the body divide uncontrollably, taking over normal tissues. About 20 percent of individuals will have skin cancer at some time in their lives. This is an increase over the past several decades because of increases in UV radiation exposure from ozone depletion. The main cause of skin cancer is DNA damage from UV radiation
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