This 16-year old girl had a several-year history of uncontrolled undiagnosed hypothyroidism. She developed generalized indurated plaques, mostly involving the extremities. Generalized myxedema often affects patients with hypothyroidism, as in this case. The pathogenesis is unknown. The histology in this case is typical with increased interstitial dermal mucin throughout the dermis, accentuated around adnexal structures. The amount of mucin varies. Definitive diagnosis rests on clinicopathologic correlation, because many conditions cause cutaneous mucinosis.
At medium power of the same lesion, spindled-to-stellate fibroblasts float within this mucinous matrix. There is no significant inflammation. An alcian blue stain confirmed the presence of mucin (not shown).