Preradial myxedema in thyroid disease.

Patients with Graves' disease were noted to have thickening of the skin on the extensor surfaces of their forearms. Skin biopsy specimens were obtained from nine consecutive patients with Graves' disease treated with sodium iodide I 131, from three patients with other thyroid disorders, and from one patient with acromegaly. Skin specimens from one patient with scleredema and one patient with scleromyxedema were used as controls for the histologic stains. Hematoxylin-eosin-stained sections of forearm skin from eight of nine patients with Graves' disease showed prominent round-cell (probably lymphocytic) infiltration around dermal capillaries and distortion of collagen fibers. In five of the patients with Graves' disease, staining with Mowry's colloidal iron disclosed dense deposits of mucin in the papillary dermis, with a distribution similar to that reported for pretibial myxedema. Mucopolysaccharide deposition in the skin on the extensor surface of the forearms may be the clinical counterpart of pretibial myxedema.