The association of different serum IgG4 levels with distinct clinical characteristics and treatment efficacy in patients with IgG4-related disease.

Objectivse To explore the clinical characteristics and treatment efficacy of IgG4-related disease (IgG4-RD) patients with different levels of serum IgG4. Methods A total of 299 patients newly diagnosed with IgG4-RD were enrolled in this study. Patients were classified into four groups according to baseline serum IgG4 levels: Group A: normal concentration; Group B: > normal but 5× the URL. All patients were followed up for 12 months. The patients' clinical characteristics, laboratory parameters, plasmablasts/plasma cells and treatment efficacy were analysed. Results IgG4-RD patients with higher serum IgG4 levels had higher percentages of dacryoadenitis, sialadenitis, and autoimmune pancreatitis and a higher prevalence of allergy history, whereas patients with retroperitoneum and mediastinum lesions usually had lower serum IgG4 levels. In addition, the serum IgG4 re-elevation rate in Group D (19.4%) was higher than those in Group B (4.9%) and Group C (7.7%) (p=0.003 and p=0.020, respectively). Patients suffered fewer clinical relapses with a serum IgG4 reduction ≥50% of baseline serum IgG4 in Group B and ≥40% of baseline serum IgG4 in Group D (p=0.019 and p=0.043, respectively). In addition, the rate of clinical relapse in patients who received combination therapy with glucocorticoids and mycophenolate mofetil was 18.75% in Group D, which was higher than the rates in Groups B and C (0) (p=0.027). Conclusions IgG4-RD patients with different levels of serum IgG4 exhibit different clinical characteristics and treatment responses.