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

IgG4 related diseases (IgG4-RD) are characterized mainly by organic dysfunction and inflammation with lymphoplasmacytic cells infiltration.

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.

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.

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.