Idiopathic Mediastinal Fibrosis: a Systemic Immune-Mediated Disorder. A Case Series and a Review of the Literature.

Mediastinal fibrosis is a rare disease characterised by fibrous proliferation in the mediastinum. It can be idiopathic or secondary to several conditions such as infections and malignancies. Anecdotal reports have described idiopathic mediastinal fibrosis (IMF) in association with other fibro-inflammatory or autoimmune diseases. We report nine new IMF cases recently seen at our Fibro-Inflammatory Disease Clinic and reviewed the IMF cases reported in the English language literature throughout 2006-2016. The purposes of our literature search were to assess the frequency of the association between IMF and other immune-mediated disorders and to analyse which disorders most often coexist with IMF. Of our nine IMF cases, one was associated with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, one with large-vessel arteritis, three with idiopathic retroperitoneal fibrosis (one of which was IgG4-related), one with pancreatitis and one with IgG4-related seminal vesicle involvement. The remaining two cases, in which IMF was not associated with any other disease, were both classifiable as IgG4-related. The literature review showed that, of the 84 IMF cases identified, 27 (32 %) were associated with other idiopathic autoimmune or fibro-inflammatory disorders, particularly small-vessel vasculitis, Behçet disease, retroperitoneal fibrosis and other conditions belonging to the IgG4-related disease spectrum. Based on our own data and the literature review, we conclude that IMF is often associated with other autoimmune or fibro-inflammatory diseases; therefore, its clinical management requires an accurate screening of associated conditions. Immune-mediated mechanisms may be shared by these disorders.