The terms lichen myxedematosus, papular mucinosis, and scleromyxedema are used interchangeably to describe the same disorder. A spectrum of disease appears to exist, with the more localized, less severe forms, which are generally called lichen myxedematosus or papular mucinosis, and the more sclerotic, diffuse form, which is 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. Sclerotic features, systemic involvement, and monoclonal gammopathy are absent in localized lichen myxedematosus.
The etiology is unknown; however, the disease is commonly associated with plasma cell dyscrasia. The basic defect is hypothesized to be a fibroblast disorder, which causes the increased mucin deposition in the skin. The cytokines interleukin (IL)–1, tumor necrosis factor (TNF)–alpha, and TNF-beta may play a role. Most patients have a monoclonal paraprotein band, usually of the immunoglobulin G (IgG) type. The association between this paraprotein and the mucin deposition is not clear, and the protein does not directly stimulate fibroblast proliferation. Paraprotein levels have not been shown to correlate with disease severity, response to therapy, or disease progression.
Persons of any race can be affected.
No sex-related predilection is reported.
Most individuals with lichen myxedematosus are aged 30-70 years.
For lichen myxedematosus, the prognosis is a chronic course with little tendency for spontaneous resolution. Although most patients have a monoclonal paraproteinemia, they rarely have associated multiple myeloma. However, when myeloma is present, the patient generally has a poor prognosis.
Scleromyxedema usually has a poorer prognosis than that of the other forms. Typical causes of death include complications of systemic therapeutic agents such as melphalan or systemic disease such as cardiovascular involvement.
Patients with cardiac or pulmonary involvement also have a poor prognosis.
Patients with lichen myxedematosus have a long-term, disfiguring, possibly disabling disorder. The risks and benefits of systemic therapy must be weighed carefully.
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