POLR3A and alopecia universalis congenita: AU patients had significantly higher serum dsDNA levels and upregulated expression of genes encoding dsDNA receptors (LRRFIP1, POLR3A, MRE11, and TLR3), ssRNA receptors (TLR8), absent in melanoma factor 2 (AIM2)‐related inflammatory factors (CASP1, IL‐1β), and interferon α and β