Tru9I Variant as a Novel Genetic Marker for Vitamin D Deficiency in Alopecia Areata.

Introduction: Alopecia areata (AA), is a common autoimmune nonscarring alopecia. Vitamin D is involved in various biological processes such as immune regulation, cellular growth, and specialization, as well as the maintenance of the hair cycle. We aimed to explore the impact of different Tru9I variant genotypes on serum vitamin D levels and vitamin D receptor (VDR) gene expression. Methods: Case-control study that included 72 individuals diagnosed with AA, along with age and sex matched healthy controls of 72 individuals. Blood samples were obtained to measure Vitamin D level and VDR gene expression focusing on Tru9I variant genotypes. Results: Our findings indicate, for the first time, a possible association between the "U" allele and low vitamin D levels, along with altered activity of the VDR gene as observed in patients with AA. Conclusion: This suggests a complex causal relationship between genetic factors and vitamin D in AA. Interestingly, "u" allele was found to be significantly more prevalent in the healthy control group than in the patients group, raising the possibility of its protective mechanism against the development of this disease in healthy individuals.