CD79A and Cowden disease: Previous studies have used endogenous IgA coating of bacteria to identify contributors to intestinal mucosal immunity, in a strategy called IgA-seq.2,14,15 More recent studies have used circulating IgG recognition of enteric bacteria to identify taxa that translocate through the intestinal mucosa.16 To identify enteric bacteria with systemic IgG reactivity in subjects with extraintestinal manifestations of CD, we adapted this approach using autologous serum and stool (rather than using a standardized set of bacteria), a protocol referred to here as IgG-Seq (Figure 2a).