02/12/2019
INHERITANCE of Vitiligo
It sometimes "runs in families," suggesting a genetic basis. However, in these families, the inheritance appears to be multifactorial, involving the interaction between multiple genes and unidentified environmental factors or triggers. This means that it is not possible to predict the chance that other family members might develop vitiligo. About 25% to 50% of people with vitiligo have a relative with vitiligo, and about 6% have siblings with vitiligo.
Variations in over 30 genes, occurring in different combinations, have been associated with an increased risk of developing vitiligo. Two of these genes are NLRP1 and PTPN22. The NLRP1 gene provides instructions for making a protein that is involved in the immune system, helping to regulate the process of inflammation. Inflammation occurs when the immune system sends signaling molecules and white blood cells to a site of injury or disease to fight microbial invaders and facilitate tissue repair. The body then stops (inhibits) the inflammatory response to prevent damage to its own cells and tissues.
The PTPN22 gene provides instructions for making a protein involved in signaling that helps control the activity of immune system cells called T cells. T cells identify foreign substances and defend the body against infection.
The variations in the NLRP1 and PTPN22 genes that are associated with an increased risk of developing vitiligo likely affect the activity of the NLRP1 and PTPN22 proteins, making it more difficult for the body to control inflammation and prevent the immune system from attacking its own tissues.
Studies indicate that variations in a number of other genes also affect the risk of vitiligo. Many of these genes are also involved in immune system function or melanocyte biology, and variations in each likely make only a small contribution to vitiligo risk. Some of the gene changes associated with an increased risk of vitiligo have also been associated with an increased risk of other autoimmune conditions.
It is unclear what specific circumstances trigger the immune system to attack melanocytes in the skin. Research suggests that the immune system of affected individuals may react abnormally to melanocytes that are stressed by factors such as chemicals or ultraviolet radiation. In addition, the melanocytes of people with vitiligo may be more susceptible to stress than those of the general population and therefore may be more likely to be attacked by the immune system. The condition probably results from a combination of genetic and environmental factors, most of which have not been identified.
