IgG4-related disease, retrospective histopathological diagnosis. Prevalence in a University Hospital.

INTRODUCTION: IgG4 related diseases (IgG4-RD) are characterized mainly by organic dysfunction and inflammation with lymphoplasmacytic cells infiltration.
METHODS: We conducted a retrospective study. We analyzed patients with a diagnosis of IgG4-RD through histopathologic registries. We divided the study into three phases: (i)extraction of data from the registries of the Pathology Department, including specimens reported with: non-specific inflammation with plasmatic cell infiltration, inflammatory pseudo-tumors and storiform fibrosis, and excluding any report of cancer or infection; (ii)from the selected specimens, three pathologists microscopically re-analyzed these biopsies and included only those who had at least two of the inclusion criteria cited above; (iii)finally, immunostaining was performed in the specimens selected in the second phase. The selected biopsies were catalogued as compatible for IgG4-RD if they had at least 3 inclusion criteria and as probable if they had 2 inclusion criteria.
RESULTS: On the first phase of the study we analyzed 23,720 biopsies, from which we included 71 and excluded 29 specimens; the rest of the specimens (n=41) underwent immunostaining. From the biopsies included, 41.4% (n=17/71) were positive to IgG4, with the most common histological diagnosis for the positive specimens being granulomatous mastitis, which represented 12.1% of the specimens catalogued initially as probable. The rest of the positive biopsies were from aortitis, dacrioadenitis and/or sialoadenitis, lung pseudo-inflammatory tumor, pericarditis and chronic pancreatitis.
CONCLUSIONS: The suspicion of IgG4 related disease should not be based solely on clinical manifestations or serology. In the present study we confirm the characteristic changes of IgG4-RD in patients without initial clinical suspicion.