Scleromyxedema, the most severe manifestation of the spectrum of lichen myxedematosus, is characterized by cutaneous mucinosis, extracutaneous manifestations, and a monoclonal gammopathy. Seven of 8 patients evaluated at our center were treated with high-dose melphalan (180 mg/m(2) intravenously) and autologous peripheral blood stem cell transplantation, with marked improvement of gastrointestinal, central nervous system, pulmonary manifestations, and Karnofsky performance status. Five patients obtained a cutaneous complete remission and 2 patients had partial remissions. Three patients with slight progression in the skin at 12, 8, and 4 months after treatment received a second cycle of high-dose melphalan and had further symptomatic improvement. The lichen myxedematosus-scleromyxedema spectrum appears to be a continuum that requires the presence of a serum paraprotein and differs in severity of skin lesions, extracutaneous manifestations, and performance status. High-dose melphalan followed by autologous transplantation appears effective for improving the symptoms and systemic manifestations of scleromyxedema.