Ultrastructural and immunological findings in Graves' disease with pretibial myxedema

This is a report on a 67-year-old female patient with Graves' disease and extensive pretibial myxedema. Linear IgM deposits were observed in the basement membrane zone by direct immunofluorescence. These deposits were found, by immunoelectron microscopy, to be haphazardly distributed in the uppermost dermis without any correlation to preexisting structures. An amorphous material that coated not only the surface of fibroblasts and collagen bundles but was also present within the dilated endoplasmic reticulum of the fibroblasts was the predominating pathological finding at the ultrastructural level. Mast cells were morphologically normal. These results support previous in vivo and recent in vitro findings indicating that the fibroblast plays a major role in the pathogenesis of pretibial myxedema.