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The Condition - Vitiligo
Vitiligo is a an autoimmune condition that causes skin depigmentation. It takes the form of skin white spots with a sharp margin and a milk white colour. The normal texture and sensation of the skin are preserved. No scaling occurs. Vitiligo spots need to be differentiated from other skin discolourations, including tinea alba and versicolour caused by fungus. Vitiligo is usually patterned and symmetrical. In some patients the spots match on both extremities in a mirror-image.
Vitiligo may either remain static for years or progress gradually, sometimes extending rapidly over a period of several months.
Vitiligo is believed to be an autoimmune disorder with a genetic basis. An autoimmune disorder is any condition in which a person's immune system reacts against the body's own tissues or organs attacking them. In the case of Vitiligo, the immune system attacks and damages or destroys melanocytes. Melanocytes are specialized skin cells that produce melanin. Melanin is the pigment that gives the skin its natural colour.
Leucoderma
Leucoderma is just another name for Vitiligo: "leuco" means white and "derma" refers to the skin (Greek root).
Causes of Vitiligo.
Vitiligo is the result of the damage or death of the skin’s melanocytes. There are different theories about the cause of Vitiligo:
The body’s immune system may destroy melanocytes. Pigment may be destroyed as the body responds to a substance it perceives as foreign (the most accepted theory).
There is genetic defect that makes the melanocytes susceptible to injury.
Abnormally functioning nerve cells may produce toxic substances that injure melanocytes.
Melanocytes self-destruction. While pigment is forming, toxic by-products could be produced injuring and destroying melanocytes.
Researchers believe that a combination of these theories may provide the best explanation.
Stress can both trigger and worsen Vitiligo.
Vitiligo’s association to other conditions.
In a small number of people it can be associated to other autoimmune, however most Vitiligo patients are in good health.
Vitiligo: inheritance & genetics
Vitiligo is sometimes passed from one generation to another. A study of twins showed that both identical twins are more likely to develop the disease than both non-identical twins. About 1 in 200 individuals get Vitiligo (North America). In families, that increases to about 5% for children or parents, and about 2-3% for grandparents. This suggests there are genetic factors that make an individual susceptible to having Vitiligo.
How is Vitiligo inherited?
It is considered to be autosomal (not linked to sex) and polygenic. Polygenic means that unlike other genetic diseases involving single genes, Vitiligo and other autoimmune diseases appear to involve many susceptibility genes. Some of these genes might be importantly related to the function of the immune system. At least in some Vitiligo patients the immune system attacks and destroy melanocytes, the pigment-producing cells of the skin. In some families it is associated to other autoimmune diseases, like thyroid disease and pernicious anaemia. One family member may have a thyroid problem and another may have Vitiligo.
Vitiligo appears to be not only polygenic (a genetic defect would make melanocytes susceptible to injury) but also multifactorial. These means that there are other factors that probably work in combination and cause the disease. These factors may include the body’s immune system that may destroy melanocytes; abnormally functioning nerve cells that may produce toxic substances that injure melanocytes; production of toxic byproducts that could injure and destroy melanocytes while pigment is forming; and environmental factors, such as infections or damage to the skin.
Vitiligo itself is not inherited, but the disposition to have it can be inherited. It is probably a combination of genes that may be the critical factor plus some stimulus capable of starting it off. In the future, a deeper knowledge of which genes are involved may allow genetic testing for individuals that might be predisposed to having Vitiligo. In those individuals environmental risk factors could be more carefully avoided in order to prevent the onset of Vitiligo depigmentation.
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