Background/Purpose: IgG4-related disease (IgG4-RD) is a widely recognized systemic inflammatory disorder. However, owing to its extremely diverse clinical picture, each clinician encounters a clinically distinct patient (pt) population depending on his/her specialty, and it is difficult to avoid institutional bias in a single center. This prompted us to conduct a relatively large-scale multicenter study with well-experienced physicians of IgG4-RD including rheumatologists, gastroenterologists, pulmonologists and nephrologists. The purpose of this study is to clarify the baseline clinical and laboratory features of IgG4-RD using a relatively large-scale cohort of 333 IgG4-RD pts.

Methods: Between 2001 and 2014, we retrospectively evaluated 333 pts with IgG4-RD in five institutions. The diagnosis of IgG4-RD was made based on the comprehensive diagnostic criteria or criteria of each organ. We analyzed the serum levels of IgG, IgG4, C3, C4, CH50 and CRP, the affected organs, the target organs for biopsy and treatment. We also determined the prevalence of diabetes mellitus (DM) and malignancy.

Results: Two hundred and four pts were male, and 129 were female (male 61.3%). The mean age was 63.8 years (range 25-91). At diagnosis, mean serum IgG and IgG4 were 2404 mg/dL and 755 mg/dL respectively. Serum IgG4 was elevated in 317 of 332 (95.5%). Hypocomplementemia was seen in 137 of 327 (41.9%), with pts with kidney lesion showing an especially high frequency (59.5% vs. 36.3%, p<0.001). Serum level of CRP was less than 1.0 mg/dL in 90.2%. Mean number of organs involved was 3.2 (range 1-11); salivary gland (SG) was the most frequently involved organ (72.3%), followed by lacrimal gland (LG), pancreas, retroperitoneum (RP)/periaorta, kidney, and lung. Single organ involvement excluding lymph nodes was seen in 63 of 333 (18.9%), with the most frequently affected organs being SG followed by LG. RP/periaorta, lung and kidney were more frequently affected in males than in females, whereas LG and SG were more frequently affected in females than in males. Biopsy was performed in 270 of 333 (81.1%), with SG 45.1%, lung 16.7%, pancreas 15.3%, kidney 15.2%. Corticosteroid therapy was administered to 248 of 313 (79.2%), and the mean initial dose of prednisolone was 30.5 mg/day. The prevalence of DM was significantly higher in those with than without AIP (47.0% vs. 30.0%, p=0.005). The prevalence of malignancy was 16.8%.

Conclusion: The present study clarified the organs most frequently affected by IgG4-RD by a retrospective multicenter study. In addition, we reconfirmed the high frequency of hypocomplementemia in pts with kidney lesion. Moreover, in more than 95% of pts, serum elevated IgG4 levels were useful for the diagnosis of IgG4-RD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/baseline-clinical-and-laboratory-features-of-igg4-related-disease-retrospective-japanese-multicenter-study-of-333-cases/