[1606] IgG4 Plasmacytosis Is a Common Histological Association in Aspergillosis

Y Iinuma, Y Kashima, S Ishizawa, R Hayashi, T Tanaka, Y Iwata, S Kageyama, M Hofer, J Fukuoka. Toyama University Hospital, Toyama, Japan; Toyama University, Faculty of Medicine, Toyama, Japan; Brigham and Women's Hospital, Boston; Harvard Medical School, Boston

Background: IgG4 related plasmacytic disease (IgG4-RPD) is a newly recognized disorder of uncertain etiology which shows various clinical and histological features. Inflammatory pseudotumor, autoimmune pancreatitis, and sclerosing cholangitis are known variants of IgG4-RPD. The common histological features seen in IgG4-RPD are abundant plasma cell infiltration along with dense hyalinizing fibrosis and frequent obliterative venulitis. Areas of chronic scarring seen in aspergillosis show similar histological patterns except the presence of cavitary lesions. To examine the histological overlap between aspergillosis and IgG4-RPD, we immunohistochemically analyzed the 13 cases of continuous cases with aspergillosis.
Design: 13 cases with aspergillosis were collected from case archive at Toyama University between 1999 and 2008 which includes eight male and six female with age ranged 48 to 90 years. Eight patients were diagnosed as chronic sinusitis. Three patients had cancer apart from the area with aspergillosis. Other two patients were diagnosed as pulmonary aspergillosis The specimens were immunostained with anti-IgG and IgG4 antibodies. We selected three fields for each specimen randomly and counted number of IgG4-positive plasma cells and IgG positive plasma cells. We calculated ratio of IgG4-positive plasma cells and IgG-positive plasma cells.
Results: All 13 cases of aspergillous infection showed marked plasmacytic infiltration along with chronic fibrosis, tissue eosinophilia, and destruction of the basic architecture, which overlap histological characteristics of IgG4-RPD. IgG4 general is the rarest component among the IgG subclasses and it only accounts for less than 6% of the total IgG fraction. In our cohort with aspergillous infection, all cases showed significant increase of IgG4 positive plasma cells in which IgG4/IgG was ranged from 39.8 to 78.8% (mean 58.3%).
Conclusions: The histological similarity between aspergillous and IgG4-RPD suggests a common pathogenetic process. Considering the vast histological variations what aspergillous infection show, our results should alert pathologists that chronic aspergillous infection should be ruled out when IgG4-RPD is considered in the differential diagnosis.
Category: Pulmonary

Monday, March 9, 2009 9:30 AM

Poster Session I Stowell-Orbison/Autopsy Award # 231, Monday Morning