Background: Alopecia areata (AA) is a non-scarring hair loss with a polymorphous presentation ranging from patchy lesions to involvement of the entire scalp. The disease is the consequence of an autoimmune attack on hair bulbs that results in a premature transition of hair follicles to catagen and telogen. Thus the Wnt/β-catenin signaling pathway that regulates the hair cycling might be involved in the pathogenesis of AA. Genetic variations in the components of Wnt/β-catenin could greatly alter their adaptive mechanisms against an immunologic attack. Objectives: Our aim was to investigate the association between AA and genetic polymorphisms in the TCF7L2 gene, one of the most important components of the Wnt/β-catenin pathway. Methods: This is a case-control study of 145 patients with AA and 152 healthy controls. Genotyping of the TCF7L2 gene (rs7903146) was performed via the ARMS-PCR method (amplification refractory mutation system- polymerase chain reaction). The allele and genotype distribution was compared between the two groups. Results: The frequency of the T allele (0.38 vs. 0.28, odds ratio = 1.56, 95% CI = 1.09-2.17, p = 0.013) and TT + CT genotypes (0.68 vs. 0.53, odds ratio = 1.88, 95% CI = 1.17-3.02, p = 0.008) were significantly higher in AA patients. Conclusions: This study indicates that the TCF7L2 gene variant is associated with AA. Its contribution to disease pathogenesis could either be through a hair cycling defect or dendritic cell dysregulation.
Keywords: Wnt signaling; autoimmunity; dendritic cell; genetic association study; hair follicle.