Clinical and pathological characteristics of IgG4-related sclerosing sialadenitis

Objectives/Hypothesis: A new concept of IgG4-related sclerosing 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 eight tissue samples from patients with IgG4-related sclerosing sialadenitis were studied. Study Design: A retrospective clinical study at Yamagata University School of Medicine. Methods: The patient group consisted of six males and four females with an average age of 60 years (range, 47-74 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 six of these patients were successfully treated with systemic corticosteroids. Conclusions: In the six patients with systemic complications, treatment with systemic corticosteroids reduced the salivary gland enlargement and lowered serum IgG4 concentrations. These results suggest that IgG4 plays an important role in the pathogenesis of IgG4-related sclerosing sialadenitis, and that IgG4 levels and IgG4/IgG ratios may be used as additional indicators of disease activity and as biomarkers for potential life-threatening complications.