The terms lichen myxedematosus, papular mucinosis and scleromyxedema have been used interchangeably to describe this disorder. There appears to be a spectrum of disease with the more localized, less severe forms, generally called lichen myxedematosus or papular mucinosis, and the more sclerotic, diffuse form referred to as scleromyxedema. Lichen myxedematosus is a rare skin disorder characterized by fibroblast proliferation and mucin deposition in the dermis, in the absence of thyroid disease. The basic defect has been hypothesized to be a fibroblast disorder, which causes the increased mucin deposition in the skin.
Most patients have a monoclonal paraprotein band, usually of the IgG type.
The association between this paraprotein and the mucin deposition is not clear, and the protein does not directly stimulate the fibroblast proliferation. Lichen myxedematosus is usually a chronic disease. Although most patients have a monoclonal paraproteinemia, they rarely have associated multiple myeloma. However, when myeloma is present the patient will generally have a poor prognosis. Patients with cardiac or pulmonary involvement also have a poor prognosis.