Investigation of IgG4-positive cell infiltration in biopsy specimens from cases of hypertrophic pachymeningitis.

This study was an immunohistological study of IgG4-positive cell infiltration in 6 cases of hypertrophic pachymeningitis excluding secondary hypertrophic pachymeningitis caused by infectious diseases such as aspergillosis. The cases included 5 males and 1 female, ranging in age from 36 to 82 years (mean, 55 years). A biopsy was performed in all of the cases for diagnostic purposes, revealing fibrous dural hyperplasia with nonspecific inflammatory cell infiltration histologically. Two of the 6 patients had been treated with steroids before the biopsy, which was taken for poor response to steroid treatment. In these two cases, some IgG-positive cell infiltration of the thickened dura was observed; however, most of the cells were IgG4-negative. In the remaining four cases, many IgG- and IgG4-positive cells infiltrated the thickened dura and the IgG4-positive/IgG-positive cell ratio exceeded 40%. One of these patients was finally diagnosed with IgG4-related sclerosing disease, since he was diagnosed subsequently with retroperitoneal fibrosis. There was no evidence of any other lesions associated with IgG4-related sclerosing disease, other than in the dura. It is not rare for IgG4-positive cells to appear in the dura in cases of hypertrophic pachymeningitis; however, no IgG4-related systemic disease is present in these cases. Hypertrophic pachymeningitis with IgG4-positive cells may have some kind of relation to other systemic autoimmune diseases.