Riedel's thyroiditis association with IgG4-related disease

Abstract

Context

IgG4 positive (+) plasma cells have been reported in both Riedel's thyroiditis (RT) and Hashimoto's thyroiditis (HT). These cells are the hallmark of IgG4-related disease (IgG4-RD).

Objective

We sought to determine if RT is part of IgG4-RD spectrum.

Design, Setting and Patients

This was a case-control study performed at a tertiary medical center. We included RT cases from the period 1958-2008 that had sufficient paraffin-embedded tissue for IgG4 immunostaining. Controls were HT patients, age and gender matched, with similar pathology criteria.

Main Outcome Measure

The main outcome measures were the intensity of the IgG4 staining and the clinical and histological correlates with IgG4-RD.

Results

Six pairs of RT and HT were analyzed. The mean age was 44.7 years. In both groups 5/6 cases had positive IgG4 staining. The mean number of IgG4+ cells/ HPF, normalized to the degree of inflammation, was 3.2 ± 3.0 SD (RT) vs. 0.9 ± 0.7 (HT), p=0.15, for fibrotic areas and 2.1 ± 2.3 SD vs. 1.0 ± 0.8 (p=0.39) for areas with lymphoid aggregates. We found the number of IgG4+ cells in RT to be inversely correlated with the duration of disease (p=0.046). Three RT cases had associated co-morbidities from the IgG4-RD spectrum while none of the HT cases had such conditions.

Conclusions

RT is a component of IgG4-RD with the density of the IgG4+ lymphocytic infiltrate being time dependent. In this small study we did not identify differences in IgG4 infiltration between RT and HT, minimizing the utility of this marker in RT diagnosis.

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