Riedel's Thyroiditis and Multifocal Fibrosclerosis are part of the IgG4‐related systemic disease spectrum

Objective Riedel's thyroiditis is a chronic fibrosing disorder of unknown etiology often associated with “multifocal fibrosclerosis.” IgG4‐related systemic disease is characterized by IgG4+ plasma cell infiltration and fibrosis throughout many organs. We hypothesized that Riedel's thyroiditis is part of the IgG4‐related systemic disease spectrum. Methods We searched our institution's pathology database using the terms “Riedel's,” “struma,”...