['We recently reported mucosal infiltration of IgG4-expressing plasma cells in a patient with chronic antibiotic-refractory pouchitis (CARP). The role of serum IgG4 in the pathogenesis and clinical course of ileal pouch disorders has not been investigated. We hypothesized that IgG4-mediated autoimmunity may be a contributing factor in for CARP. The aims of the study were to investigate the prevalence of elevated serum IgG4 in symptomatic patients with ileal pouches and to characterize clinical features of pouch disorders in these patients.', 'A total of 124 consecutive symptomatic patients with ileal pouches from our subspecialty Pouchitis Clinic were enrolled in the study from January to October 2010. Serum IgG4 was measured at the time of presentation. Demographic, clinical, and laboratory characteristics were compared between the study (with serum IgG4 ≥112 mg/dl) and control (with serum IgG4 <112 mg/dl) groups.', "There were ten patients (8.0%) with high serum IgG4 in the study group, while the remaining 114 (92%) patients were in the control group. The prevalence of elevated serum IgG4 in this series was 8%. None of the patients had a confirmed diagnosis of autoimmune pancreatitis. The median serum IgG4 in the study group was 144.5 vs. 14 mg/dl in the control group. The mean age of patients in the study and control groups was 35.5 ± 14.5 and 42.0 ± 13.2 years, respectively (p = 0.137). Two patients in the study group (20.0%) had concurrent autoimmune disorders as compared to 19 patients (16.7%) in the control group (p = 0.788). Three (30.0%) patients in the study group had coexisting primary sclerosing cholangitis (PSC) in contrast to 15 (13.2%) in the control group (p = 0.147). Among the study group patients, five (50.0%) had CARP and one (10%) had Crohn's disease (CD) of the pouch, while in the control group, 23 (20.2%) had CARP and 24 (21.1%) patients had CD of the pouch (p = 0.273). CARP was more commonly seen in patients with high serum IgG4 than patients with a normal IgG4 (50.0% vs. 20.2%, p = 0.03)."] Is elevated serum IgG4 associated with chronic antibiotic-refractory pouchitis?