IgG4-positive Cell Quantification Distinguishes Between Inflammatory and Noninflammatory Diseases of the Orbit.

IgG4-related ophthalmic disease (IgG4-ROD) is a rare inflammatory disorder often refractory to corticosteroids and prone to recurrence. IgG4-ROD may frequently lack the characteristic histopathological features seen in other organs. Thus, the criteria for diagnosis of IgG4-ROD relies on elevated IgG4 cells seen on biopsied tissue. Proposed threshold levels of IgG4 to diagnose IgG4-ROD are currently based on a limited understanding of this cell type's presence in the orbit. This study seeks to describe the population of IgG4 in inflammatory and noninflammatory orbital tissues. A tertiary care center's pathology database was searched with keywords "orbit" or "orbital" from 1995 to 2013. Specimens meeting the selection criteria were evaluated, and regions of highest inflammation were identified and immunostained with IgG4 and CD138 antibodies. Immunohistochemical quantification proceeded as previously established by the international consensus criteria. Eighteen cases without a history of orbital inflammation were included as controls and were evaluated as above. Specimens from 68 inflammatory and 18 noninflammatory orbits met the selection criteria. Pathologist interreader correlation coefficient on quantification was >0.70 (P<0.001). The mean IgG4+/high powered field (HPF) and IgG4+/CD138 was 10.3 and 0.1 in inflammatory tissues and 0.5 and 0.01 in noninflammatory tissues, respectively. The spearman rho correlation coefficient between IgG4/HPF and IgG4+/CD138+ was >0.95 (P<0.0001). The mean IgG4/HPF in our study reached previously proposed threshold values for diagnosis of IgG4-ROD, illustrating the need for further discussion regarding diagnostic criteria of IgG4-ROD.