Ultrastructure of localized myxedema.

Five biopsies from three patients with localized myxedema were studied by electron microscopy. The dermis showed an overwhelming accumulation of microfibrils with knobs (acid glycosaminoglycans) and an amorphous material containing glycoprotein. Furthermore, evidence of degradation without new formation of collagen fibrils was found. Considerable numbers of mast cells with various types of granules, fibroblasts with dilated granular endoplasmic reticulum, and macrophages were seen in the mucinous areas.