Hypocomplementemia is related to elevated serum levels of IgG subclasses other than IgG4 in IgG4-related kidney disease

Abstract

Objectives

This study investigated the clinical features of IgG4-RKD patients with hypocomplementemia compared with those without it, so as to clarify the factors related to hypocomplementemia.

Methods

In this single-center retrospective study, we analyzed the clinical features of 25 patients with IgG4-RKD according to the presence/absence of hypocomplementemia. Additionally, we validated the results of a single-center study in a separate large multicenter cohort of 328 patients with IgG4-RD, and searched for factors related to hypocomplementemia.

Results

Serum IgG levels (p < .001), non-IgG4 IgG levels, calculated as the total IgG minus IgG4 (p < .001), serum IgG1 levels (p = .017), and the number of involved organs (p = .018) were significantly higher in the hypocomplementemia group. At relapse of renal lesions in four patients, all had serum IgG4 re-elevation, with the three with hypocomplementemia presenting worsening of hypocomplementemia and re-elevation of non-IgG4 IgG levels. In a validation cohort of 328 patients with IgG4-RD, multivariate logistic regression analysis indicated elevation of non-IgG4 IgG levels to be an independent factor related to hypocomplementemia in the patients with IgG4-RKD.

Conclusion

The present study suggests that hypocomplementemia is associated with elevation of IgG subclasses other than IgG4 including IgG1 in IgG4-RKD.

Keywords:

• Hypocomplementemia
• IgG4-related kidney disease
• IgG subclass

Acknowledgements

We thank John Gelblum for his critical reading of the manuscript.

Author contributions

Y.F., I.M., and M.K. designed the research; Y.F., I.M., K.Y., M.Y., T.S., S.M., S.T., S.H., K.I., H.F., H.T., S.K., and S.K. acquired data; Y.F., I.M., H.N., and M.K. analyzed the data; Y.F. and I.M. drafted the manuscript: All authors interpreted the results, revised the drafts, and approved the final version.

Conflict of interest

None.

Additional information

Funding

This work was supported partially by Health and Labour Sciences Research Grants for the Study of Intractable Diseases from the Ministry of Health, Labor and Welfare, Japan, JSPS KAKENHI [Grant Numbers 26461487 and 17 K09999].