IgG4-related disease with epithelioid granulomas: a case and a review of the literature.

IgG4-related disease (IgG4-RD) is a systemic, immune-mediated, fibroinflammatory disorder that affects multiple organs. Histopathologically, the supportive findings of IgG4-RD include dense lymphocytic infiltrates, obliterative phlebitis, storiform fibrosis, and elevated numbers of IgG4-positive plasma cells. However, the presence of granulomatous inflammation is generally considered highly atypical, suggesting alternative diagnoses such as sarcoidosis and lymphoma. Here, we present a case of IgG4-RD involving granulomatous lymphadenopathy. Labial salivary gland biopsy findings were consistent with IgG4-related sialadenitis. Elevated serum IgG4 levels, hypocomplementemia, and abnormal imaging findings in the kidneys and pancreas indicated an association with IgG4-RD. The patient was treated with prednisolone, which resulted in a significant improvement in the serum IgG4 and complement levels and a notable reduction in lymph node swelling. Although granulomatous inflammation is rare, integrating clinical, serological, radiological, and pathological parameters can ensure an accurate assessment within the appropriate clinicopathological context.