Skin, abnormally dark or light

Alternative names:

hypermelanosis; hyperpigmentation; melanosis

Definition:

Skin that has turned darker or lighter than normal and the change is unrelated to sun exposure. See also skin color, patchy.

Considerations:

Normal skin contains cells called melanocytes that produce the brown skin-coloring pigment melanin. There are several conditions in which melanocytes are either abnormal or abnormally distributed. Most skin conditions that cause discoloration are harmless.

A pale area of the skin is the result of fewer or less active melanocytes than usual, whereas, a darker area (or area that tans more easily) indicates more numerous or more active melanocytes.

Sometimes mistaken for a suntan, bronzing of the skin often develops gradually starting at pressure points such as the elbows, knuckles, and knees and spreading from there. It is also seen in the creases of the soles of the feet and the palms of the hands. The bronze color can range from light to dark (in fair skinned people) with the intensity often a function of the underlying cause.

There are several types of benign hyperpigmentation that occur normally; however, any persistent hyperpigmentation that has not been medically explained ought to be seen by a dermatologist.

Common causes:

• exposure to the sun or sun lamp
• inherited skin condition
• phenothiazine drug use
• chronic nutritional deficiency

Note: There may be other causes of hyperpigmentation and hypopigmentation. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as location, quality, time course, aggravating factors, relieving factors, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for hyperpigmentation and hypopigmentation, occurring alone or in combination with other problems.