Background/Purpose: 　IgG4-related disease (IgG4-RD) is not rare and clinically important disease. It is difficult to confirm the diagnosis because IgG4 positive lymphocyte infiltrates various organs. Especially, lymphadenopathy is a common manifestation in IgG4-RD. However, it is difficult for the rheumatologist to distinguish its lymphadenopathy from non IgG4-RD. Elevated serum IgG4 level did not decide diagnosis of IgG4-RD. In 2011, comprehensive diagnostic criteria for IgG4-RD were established by Umehara et al. [1]. This criteria required histopathological findings to diagnose IgG4-RD definite. Recent research has shown FDG-PET/CT is useful modality to select biopsy site [2].

Methods: We enrolled 29 cases which suspected IgG4-RD with lymphadenopathy in our facility between 2008 and 2016. Serum IgG4 level was analyzed all patients which were undertaken whole-body FDG-PET/CT study and biopsy. The diagnosis for IgG4-RD was based on comprehensive diagnostic criteria for IgG4-RD. Laboratory data were retrospectively collected from their medical records. We investigated levels of serum C-reactive protein (CRP) and serum albumin, eosinophil/leukocyte ratio, serum IgG and IgG4 levels, sIL2-R levels, the size and maximum standardized uptake value (SUVmax) and distribution of lymph nodes with abnormal FDG uptake on FDG-PET/CT and pathological findings. We investigate the utility of FDG-PET imaging and serological biomarkers for diagnosing lymphadenopathy of IgG4-RD.

Results: 　29 patients were diagnosed into 3 groups (IgG4-RD definite: 12, IgG4-RD possible: 10, non IgG4-RD: 7). Non IgG4-RD group was included infectious disease, systemic lupus erythematosus, eosinophilic granulomatosis with polyangiitis, Sjogren’s syndrome, Castleman’s disease, and malignant lymphoma. No significant differences among 3 groups in levels of CRP or sIL-2R were found. In IgG4-RD definite group, serum IgG4 levels and serum IgG4/IgG ratio were higher than other groups. Serum albumin levels were lower in non IgG4 group compared to others. Eosinophil/leukocyte ratio was higher in IgG4-RD definite group than in possible group. We examined about lymph nodes with abnormal FDG uptake. In IgG4-RD definite group, size of lymph nodes were smaller compared to other 2 groups. There is no difference among 3 groups in SUVmax or distribution of abnormal lymph nodes. Lymph node biopsy were performed in 5 patients with IgG4-RD. In 2 patients who diagnosed IgG4-RD definite, sIL-2R levels were higher and size of abnormal lymph nodes were smaller compared with those in 3 patients diagnosed IgG4-RD possible.

Conclusion: In this study, we examined patients which suspected IgG4-RD with lymphadenopathy. Patients with IgG4-RD definite tended to show higher serum IgG4 levels and smaller size of lymph nodes with abnormal FDG uptake on FDG-PET/CT. No significant differences were found among 3 groups in levels of serum CRP, sIL2-R, SUVmax or distribution of lymph nodes with abnormal FDG uptake. References: [1]Umehara H, Okazaki K, Masaki Y, et al. Comprehensive diagnostic criteria for IgG4-related disease (IgG4-RD), 2011. Mod Rheumatol. 2012 Feb;22(1):21-30. [2]Nakatani K. Utility of FDG PET/CT in IgG4-related systemic disease Clin Radiol. 2012 Apr;67(4):297-305.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/utility-of-fdg-pet-imaging-and-serological-biomarkers-for-diagnosing-lymphadenopathy-of-igg4-related-diseas/