IgG4‐Related Sialadenitis: Pearls and Pitfalls in Management

Abstract

Objective: A new concept of IgG4-related sialadenitis characterized by high serum IgG4 levels and tissue infiltration of IgG4-expressing plasmacytes has recently been proposed. To determine appropriate serum levels of IgG4 for monitoring disease activity, a total of 36 serum samples and 8 tissue samples from patients with IgG4-related sialadenitis were studied. Method: The patient group consisted of 6 men and 4 women with an average age of 60 years (range, 47 to 74 years). Serum levels of IgG4 and the density of IgG4-positive plasmacytes in affected tissues were studied. Results: All patients had elevated serum IgG4 levels (>135 mg/dL), and IgG4-positive plasmacytes (IgG4+ plasma cells/IgG+ plasma cells >50%) were observed in the involved salivary glands. Six patients with IgG4-related sclerosing sialadenitis with high IgG4/IgG ratios and prominent infiltration of IgG4-positive plasmacytes in the involved salivary glands had systemic complications, including pancreatitis, retroperitoneal fibrosis, and/or inflammatory pseudotumor of the lung after swelling of the salivary glands. All 6 of these patients were successfully treated with systemic corticosteroids. Conclusion: In the 6 patients with systemic complications, treatment with systemic corticosteroids reduced the salivary gland enlargement and lowered serum IgG4 concentrations. These results suggest that IgG4 levels and IgG4/IgG ratios may be used as additional indicators of disease activity and as biomarkers for potential life-threatening complications.