OP0110 The utility of fluorodeoxyglucose-positron emission tomography for IgG4-related disease diagnosed accorgding to comprehensive diagnostic criteria
Authors: J. Danjo, H. Dobashi, T. Kameda, K. Susaki, Y. Yamamoto, S. Nakashima, H. Shimada, M. Izumikawa, Y. Nishiyama, T. Matsunaga
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> IgG4-related disease (IgG4-RD) is a systemic disease characterized by elevated levels of serum IgG4 (sG4) and mass-forming lesions infiltrated with IgG4-positive (IgG4+) plasma cell. To date in our facilities, IgG4-RD patients has been diagnosed as autoimmune pancreatitis (AIP), Mikulicz disease (MD) or IgG4-related kidney disease (IgG4-related KD) using the conventional organ-specific criteria respectively. However, in 2012, Umehara et al. proposed comprehensive diagnostic criteria for IgG4-RD (CDC IgG4-RD)<sup>1)</sup>. Using this new comprehensive diagnostic criteria could diagnosed as IgG4-RD in some patient population that did not meet the conventional organ-specific criteria. On the other hand, there still exists important problem for the diagnosis of IgG4-RD about the requirement of histopathological evaluation. Histopathological proof is considered to need for the definitive diagnosis of IgG4-RD. Indeed clinically, there are some IgG4-RD patients diagnosed without histological findings. Additionally, pathological findings obtained from IgG4-RD patients diagnosed clinically could not reveal the typical findings with infiltration of IgG4+ plasma cell. Therefore, histopathological findings are quite important to meke a diagnosis of definitive IgG4-RD. Although the usefulness of fluorodeoxyglucose-psitron emission tomography (FDG-PET) is described in CDC IgG4-RD, it is unclear how to use FDG-PET for diagnosis of IgG4-RD. We focused on the usefulness of FDG-PET for diagnosis of definitive IgG4-RD at the point of making a biopsy-site decision. <h3>Objectives</h3> (1)To examine the diagnostic effectiveness of CDC IgG4-RD compared with conventional organ-specific criteria. (2)To determine the usefulness of FDG-PET for diagnosis of definitive IgG4-RD. <h3>Methods</h3> We examined suspected IgG4-RD patients that visited our facilities between August 2009 and November 2011 retrospectively. We obtained several information including physical findings, biochemical findings, sG4 level, and histopathological findings in each patients. These patients are analyzed using CDC IgG4-RD retrospectively. FDG-PET studies were performed in 10 IgG4-RD patients. For image evaluation, we used SUVmax that is the maximum value among the abnormal accumulation. In definitive IgG4-RD patients, we also investigated the relationship between FDG accumulation and histopathological findings in biopsy site. <h3>Results</h3> IgG4 levels were measured in 158 patients suspected for IgG4-RD, and 36 patients had high sG4 titers. Twelve cases were fulfilled to the conventional organ-specific criteria respectively (AIP, 2 cases; MD, 7 cases; IgG4-related KD, 3 cases; diagnostic rate, 7.6%). In contrast, 31 cases satisfied CDC IgG4-RD (definite, 12 cases; possible, 19 cases). FDG-PET was performed in 10 cases of IgG4-RD. In pathological examination in definitive IgG4-RD patients, IgG4+ plasma cell infiltration was demonstrated at the site of FDG accumulation. <h3>Conclusions</h3> CDC IgG4-RD might improve the diagnostic sensitivity for IgG4-RD. FDG-PET might be useful for determine the biopsy site to make a diagnosis for definitive IgG4-RD patients. <h3>References</h3> [1]Mod Rheumatol. 2012 Jan 5. [Epub ahead of print] <h3>Disclosure of Interest</h3> None Declared