IgG4-Related Disease

IgG4-related disease (IgG4-RD) is a novel clinical disease entity characterized by an elevated serum IgG4 concentration and tumefaction or tissue infiltration by IgG4-positive plasma cells. IgG4-RD encompasses a wide variety of diseases, formerly diagnosed as Mikulicz's disease (MD), autoimmune pancreatitis (AIP), hypophysitis, Riedel thyroiditis, tubulointerstitial nephritis, prostatitis, retroperitoneal fibrosis, inflammatory aortic aneurysm and inflammatory pseudotumor. However, like a crow flying on a dark night, IgG4-RD passed through the history of medicine, until the concept of an overarching of these systemic disorders was established in Japan at the beginning of the present century. In addition, most clinical practitioners are not yet familiar with IgG4-RD, and thus one cannot diagnose what one does not know. The purpose of the book [1] is to raise awareness of this disease and its diagnostic pitfalls. Another goal was to delineate the characteristic features of individual organs in IgG4-RD radiologically and histopathologically with many color photographs. Most of the authors are members of the IgG4 team of the Japanese the Ministry of Health, Labor and Welfare (MHLW), and experts who have published numerous important papers in the field. Thus, this book will be useful to physicians in various disciplines such as gastroenterology, rheumatology, ophthalmology, otolaryngology, urology, hematology, respiratory medicine and oral medicine, not only as a textbook but also as an authoritative and comprehensive reference work.

Over the past decade and with increasing pace in the last few years, a "new" disease has emerged, gradually affecting a wide range of medical specialties and explaining a host of conditions previously regarded as separate entities. is newly recognized condition is IgG4-related disease (IgG4-RD), a potentially multiorgan disorder that is characterized by elevated serum IgG4 concentrations in the majority of cases. IgG4-RD was recognized in modern times in Japan through a series of seminal observations that occurred during the 1��0s and the �rst few years of this century [1][2][3][4][5], but it is clear in reviewing the medical literature that IgG4-RD has been present and reported upon in various guises going back at least to the 1800s [6][7][8][9][10][11].
In addition to the frequent elevations of serum IgG4 concentrations, certain major pathologic hallmarks are generally present to one degree or another across all organ systems, providing the principal foundation for the belief that the disparate organ manifestations associated with this diagnosis are in fact part of the same systemic disease. ese pathologic features include a lymphoplasmacytic in�ltrate with a high percentage of plasma cells within the lesion staining for IgG4; a peculiar pattern of �brosis known as "storiform" �brosis; a tendency to affect veins in a manner that leads to obliterative phlebitis; and mild to moderate tissue eosinophilia [12].
IgG4-RD appears to sit at an intersection between different in�ammatory pathways. �any but not all patients have substantial allergic or atopic histories, and early indications are that a "modi�ed" 2 response is critical to this condition [13]. Other patients also develop tumefactive lesions leading to misdiagnoses of cancer. Still others have clinical manifestations and serological �ndings that lead to erroneous classi�cations of their diagnoses as "connective tissue diseases. " e full links between the various in�ammatory players in this symphony of in�ammation remain to be fully elucidated. It is likely that a broader understanding of the ways in which B and � cells, �broblasts, plasma cells, immune complexes, and other elements interact in IgG4-RD will provide important insights into the nature of its individual in�ammatory constituents and the broader immune system.
IgG4-RD is now recognized as a worldwide disease [14]. e international community convened in Boston in 2011 to compare notes, share experiences, and plan ways for moving ahead in understanding this condition. Building upon crucial earlier work in Japan, consensus papers pertaining to the nomenclature of this condition and to its pathological features have been published [12,15]. Japanese investigators have also published diagnostic criteria for IgG4-RD [16].
In this special issue, we are pleased to present more than two dozen papers on IgG4-RD that address a number of facets International Journal of Rheumatology of this condition: from its clinical manifestations to its radiologic features; from its pathology hallmarks to its serologic characteristics; and from its diagnostic challenges to early indications of treatment success. ese papers capture the essence of IgG4-RD in 2012 and represent the current stateof-the-art against which future advances will be compared.