A 66-year-old man presented with Graves' disease and widespread localized myxedema. Extensive lesions were present on the legs, feet, hands, and face. TSH receptor antibody (TBII) was markedly positive and the serum hyaluronic acid level was very high. Intravenous steroid pulse therapy was followed by oral therapy with gradual tapering. This regimen markedly improved the skin lesions and resulted in a decrease of the serum hyaluronic acid level. The findings suggest that steroid pulse therapy is effective for the treatment of extensive localized myxedema. In addition, the serum hyaluronic acid level may be a useful parameter for the follow-up of patients with this condition.