<qa>  What is a T-Cell mediated, non-scarring, polygenicAlopecia Areata AA is a T-Cell mediated, non-scarring, polygenic, autoimmune disease of the hair follicle. It has been reported to be associated with other autoimmune diseases, especially autoimmune thyroid disease and vitiligo. It is more common in females. Recently, vitamin D deficiency has been claimed to contribute to the pathogenesis of multiple autoimmune disease. There is a strong inverse correlation between the level of 25-hydroxyvitamin D levels and the autoimmune disease in adolescents. 