Skin color - patchy

Irregular or patchy discoloration of the skin can be caused by variations in pigment (melanin) density, blood vessel (vascular) changes, or growth of foreign organisms on the skin. Mottling or mottled skin refers specifically to vascular changes in the skin which cause a patchy appearance.

Dyschromia; Mottling

Melanin is a pigment produced in the skin cells that causes skin coloration. An amino acid, tyrosine, is converted to melanin through a series of complex chemical steps in the skin cells. This process may be affected by heredity, heat, trauma, solar or ionizing radiation, heavy metals, and other factors. Pigment production and distribution in the body is regulated in part by hormones.

Changes in any of these factors can result in hyperpigmentation (increase in pigment production), hypopigmentation (decrease in pigment production), or both. The changes may be temporary or permanent. Pigment changes can be primary (existing as a separate disorder) or secondary to (resulting from) other disorders.

A person's degree of skin pigmentation determines, to some extent, the various dermatological diseases to which a person may be susceptible. Lighter-skinned people are more sensitive to sun exposure and damage and the subsequent development of skin cancer (basal cell carcinoma, squamous cell carcinoma and malignant melanoma). Excessive sun exposure is a risk factor even for darker-skinned people.

Generally, pigment changes are cosmetic and do not affect physical health. However, psychological stress can occur because of pigment changes. Some pigment changes may indicate a risk for other disorders.

• sunburn or sun tan
• uneven application of sunscreen resulting in areas of burn, tan, and no tan
• cuts, scrapes, wounds, insect bites and minor skin infections
  • skin discoloration during the healing process
  • with time, the skin coloring generally returns
  • In darker-skinned people skin damage may cause permanent hyperpigmentation
• moles (nevi) and bathing trunk nevi or giant nevi
• malignant melanoma
• cafe-au-lait spots
• Mongolian blue spots
• vitiligo
• pityriasis alba (small circular pale spots on a child's face, usually the cheeks, often noticeable in the summertime when the skin is tanned)
• tinea versicolor
• erythrasma
• mask of pregnancy (also called chloasma or melasma, a dark brown discoloration of the cheeks and the forehead of pregnant women or those using oral contraceptives)
• photosensitivity as a reaction to medications or certain drugs
• radiation therapy