Scientists supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) have identified loci on four chromosomes that appear to play a role in the development of alopecia areata, a common autoimmune disease characterized by patchy hair loss that can eventually affect the whole scalp or, in rarer cases, the entire body. Their finding is reported in the February 2007 issue of the American Journal of Human Genetics.
Despite its high prevalence and visibility, alopecia areata is not well understood, says Angela M. Christiano, Ph.D., professor of dermatology and genetics and development at Columbia University Medical Center and lead author of the study. "Scientists have long debated whether the primary defect is in the hair follicle, the body's immune response, or both," she says. Research into the disease in recent years has suggested that the hair follicles are an immune-privileged site (meaning they are protected from being recognized as foreign by the immune system). Alopecia areata occurs when a breakdown in immune privilege allows immune cells called T lymphocytes to destroy the hair follicles, she says.
Current evidence suggests that alopecia areata is likely to be a multifactorial genetic disease. Scientists have found, for example, that when one identical twin has the disease, the other twin has a 55 percent chance of having it. Another observation is that people with immediate family members with alopecia areata have 10 times the normal risk for developing the disease themselves. Therefore, the disorder should be amenable to genetic linkage studies.
To study the genetic basis of the disease, Christiano and her colleagues recruited members of 20 families in the United States and Israel in which multiple members had been diagnosed with alopecia areata. Many of the families from the U.S. were collected through the NIAMS-supported Alopecia Areata Registry, under the direction of Madeleine Duvic, M.D. Of the 220 family members studied, 102 had the disease. Using genome-wide linkage techniques, the researchers identified at least four susceptibility loci on chromosomes 6, 10, 16 and 18 in those affected family members. "Interestingly, the major loci on chromosomes 16 and 18 coincide with loci for psoriasis that other research teams have reported," says Christiano. "Our results suggest that these regions may harbor genes involved in a number of different skin and hair disorders."
Christiano, who has alopecia areata herself, says the new findings have broad implications. Understanding the genetic factors underlying the disease would help scientists better understand the mechanisms responsible for the disease. That, in turn, could lead to treatments. "Currently, there are no effective treatments for alopecia areata," says Christiano. "Finding responsible genes could enable scientists to develop new therapies that could be tested in a mouse model, or even facilitate the development of engineered models that could be used for testing new treatments. Eventually, this could lead to the design of new treatment strategies for people--like myself--with this common and often emotionally devastating disease."
Alopecia areata affects more than 4.5 million Americans of both sexes and of all ages and ethnic groups. While the physical damage of the disease is largely cosmetic, it can have a significant impact on one's self-esteem and quality of life.
The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the Department of Health and Human Services' National Institutes of Health, is to support research into the causes, treatment, and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at (301) 495-4484 or (877) 22-NIAMS (free call) or visit the NIAMS Web site at http://www.niams.nih.gov.
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Martinez-Mir A, et al. Genomewide scan for linkage reveals evidence of several susceptibility loci for alopecia areata. Am J Hum Genet. 2007;80:316-328.