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International Journal of Rheumatology
Volume 2012 (2012), Article ID 121702, 6 pages
Research Article

Increased IgG4-Positive Plasma Cells in Granulomatosis with Polyangiitis: A Diagnostic Pitfall of IgG4-Related Disease

1Division of Anatomic Pathology, Mayo Clinic, Rochester, MN 55905, USA
2Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN 55905, USA

Received 1 December 2011; Revised 15 February 2012; Accepted 16 February 2012

Academic Editor: Yoh Zen

Copyright © 2012 Sing Yun Chang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Granulomatosis with polyangiitis (Wegener’s) (GPA) may mimic IgG4-related disease (IgG4-RD) on histologic examination of some biopsies, especially those from head and neck sites. IgG4 immunostain is often performed in this context for differential diagnosis with IgG4-RD. However, the prevalence of IgG4+ cells in GPA has not been explored. We examined the IgG4+ cells in 26 cases confirmed as GPA by a thorough clinical and pathologic assessment. Twenty-six biopsies consisted of 14 sinonasal/oral cavity/nasopharynx, 7 orbit/periorbital, 3 lung/pleura, 1 iliac fossa/kidney, and 1 dura specimens. Eight of 26 (31%) biopsies revealed increased IgG4+ cells (>30/HPF and >40% in IgG4+/IgG+ ratio). The IgG4+ cells and IgG4+/IgG+ ratio ranged 37–137/hpf and 44–83%, respectively. Eight biopsies with increased IgG4+ cells were from sinonasal or orbital/periorbital sites. In conclusion, increased IgG4+ cells are not uncommonly seen in sinonasal or orbital/periorbital biopsies of GPA, which could pose as a diagnostic pitfall.