IgG4-Related Disease and Retroperitoneal Fibrosis

Abstract

IgG4-related disease (IgG4-RD) has been observed to affect almost every organ system, with consistent histopathologic findings across systems. IgG4-RD can mimic malignant, infectious, and inflammatory disorders; accordingly, consideration of the histopathologic features of tissue biopsies and rigorous clinicopathologic correlations are essential to avoid misdiagnosis. Since the early 2000s, IgG4-RD has increasingly been recognized as a cause of what was previously referred to as “idiopathic” retroperitoneal fibrosis (RPF), and this IgG4-related RPF is now considered to comprise an important subset of IgG4-RD. This review includes an overview of IgG4-RD and discusses the pathology, pathophysiology, and clinical manifestations of IgG4. IgG4-related RPF is also discussed in this review, with topics including IgG4-related RPF versus RPF of other causes, the differences between RPF and other subsets of IgG4-RD, and treatment of both IgG4-RD and IgG4-related RPF. Figures show the histopathology features of IgG4-RD, immunostaining of tissue for IgG4, IgG4-related RPF and chronic periaortitis, “Mikulicz disease”, IgG4-RD of the lung, IgG4-related renal disease, and type 1 (IgG4-related) pancreatitis. The table lists conditions known previously by other names that often fall within the spectrum of IgG4-RD. This review contains 7 highly rendered figures, 1 table, and 66 references.