[1527] Identification of IgG4 Positive Plasma Cells in Recurrent Idiopathic Orbital Inflammation but Not in Non-Recurrent Lesions

GR Kolar, GJ Harocopos, ME Smith, SK El Mofty. Washington University School of Medicine, St. Louis, MO

Background: Idiopathic orbital inflammation (IOI) (inflammatory pseudotumor) is a rare entity that consists of chronic inflammatory cells with myofibroblasts in variable proportions that results in a variety of ocular manifestations including decreased and even loss of vision. IOI is typically steroid responsive but some require surgery. Recurrence is common; however, specific histopathologic features predictive of recurrence have not yet been identified. IgG4+ plasma cells have been detected in IOI and in some pseudotumors in various other locations, and high serum levels of IgG4 are associated with systemic syndromes. The purpose of this investigation was to evaluate the prevalence of IgG4 positive plasma cells in IOI and to identify its clinical significance.
Design: 25 cases diagnosed as IOI or orbital inflammatory pseudotumor from 1988 to 2008 comprising 16 patients were retrieved from departmental files. Sections were cut and stained with a mouse anti-human monoclonal antibody to IgG4. Normal human tonsils were used as positive control. If any cells with cytoplasmic/plasma membrane reactivity for IgG4 in10 high powered fields (HPF; 40X) were found, the specimen was considered positive for IgG4. Statistics were performed using a Fisher two tailed t test.
Results: Among the 25 unique biopsies with a histological diagnosis of IOI, 16 (in 10 out of 16 patients) had IgG4+ plasma cells. Of these 10 patients with an IgG4+ biopsy at any time during their series, 6 patients had recurrent lesions (sensitivity=100%, specificity=60%, p=0.03). None of the IgG4 negative cases recurred (negative predictive value (NPV)=1, p=0.03, 95% CI= 0.52 to 1). A positive predictive value of 0.73 was obtained when the threshold was raised to 20 IgG4+ cells/10 HPF (p=0.04). Only one patient with recurrent IOI presented with an IgG4 negative biopsy on the first specimen (sensitivity=83%, specificity=60%, NPV=0.86, p=0.15).
Conclusions: The absence of IgG4+ plasma cells is a strong predictor of the lack of future recurrence of IOI requiring surgical treatment. This finding may have potential implications for clinical diagnostics and pathophysiology of IOI.
Category: Ophthalmic

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 210, Tuesday Morning