An ultrastructural study of pretibial myxedema utilizing improved ruthenium red stain.

A case of pretibial myxedema associated with Graves' diseases has been studied by electron microscopy utilizing an improved ruthenium red stain. An organized network of microfibrils with knobs were found within the widened interfibrous spaces. This network was clearly demonstrated by the ruthenium red stain, but only a weak trace could be observed when conventional staining techniques were utilized. Knobs of the network seemed to be composed of ruthenium red-positive granules which surrounded normal fibers and granules of degrading collagen fibers. Many fibroblasts showed dilated rough endoplasmic reticulum containing much amorphous material which indicated a significant role of fibroblasts in the pathogenesis of this disease.