FCER1A and Autoimmunity: When defined if CSU patients had at least 1 positive result to ASST or ANA, the autoimmune CSU group had significantly lower ratio of IgG/IgA to FcεRIα than the non-autoimmune CSU group (the median values of IgG to FcεRIα, 0.73 [IQR 0.68–0.81] vs. 0.78 [IQR 0.72–0.89], P<0.05; the median values of IgA to FcεRIα, 0.93 [IQR 0.87–1.01] vs. 0.99 [IQR 0.93–1.05])(P<0.05, Fig 2).