As the −129C > T polymorphism is in the core promoter region of AHR gene and is juxtaposed 5′ to the SP1 recognition sequence, we therefore hypothesized that the AHR −129C > T polymorphism could influence its transcription and downstream effectors in melanocyte biology or immune system, which could further affect the development of vitiligo. The gene discussed is SP1; the disease is vitiligo.