Background
The terms lichen myxedematosus (LM), papular mucinosis, and scleromyxedema are used interchangeably to describe the same disorder. Lichen myxedematosus is a rare chronic skin disorder characterized by fibroblast proliferation and mucin deposition in the dermis, in the absence of thyroid disease.
Lichen myxedematosus has three variants:
-
Scleromyxedema
-
Localized lichen myxedematosus
-
Intermediate lichen myxedematous
Scleromyxedema is the most severe form of LM characterized by diffuse/generalized, papular and sclerodermoid eruptions with monoclonal gammopathy and systemic manifestations, some potentially fatal. The systemic manifestations of scleromyxedema include neurologic (e.g., carpal tunnel syndrome, sensory and motor neuropathy), cardiovascular (e.g., congestive heart failure, ischemia, heart block), and gastrointestinal (dysphagia) manifestations. Scleromyxedema is diagnosed based upon clinical, pathological and laboratory findings. A diagnosis is confirmed when at least three of the following criteria are met [1] :
-
Presence of generalized papular and sclerodermoid manifestations.
-
Microscopic triad (mucin deposition, fibrosis, irregular fibroblast proliferation)
-
Monoclonal gammopathy
-
Absence of thyroid disorder.
Localized lichen myxedematosus is characterized by local papular eruption only. Systemic symptoms, gammopathy and sclerodermoid findings are absent. There are five subtypes [2] :
-
Discrete papular LM
-
Acral persistent papular mucinosis
-
Self-healing papular mucinosis
-
Papular mucinosis of infancy
-
Nodular LM
Intermediate lichen myxedematous is characterized by LM with atypical or mixed features of localized lichen myxedematosus and scleromyxedema. The subtypes include the following [2] :
-
Scleromyxedema without monoclonal gammopathy
-
Localized LM with monoclonal gammopathy and/or systemic symptoms other than HIV infection
-
Localized LM with mixed features of different subtypes
Pathophysiology
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.
Epidemiology
Race
Persons of any race can be affected.
Sex
No sex-related predilection is reported.
Age
Most individuals with lichen myxedematosus are aged 30-70 years. Rarely, cases of lichen myxedematosus have been reported in children and adolescents. [3, 4] A variant specific to children, cutaneous mucinosis of infancy, was first identified in 1980 and there have been less than 20 cases reported since. [5]
Prognosis
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.
Patient Education
Patients with lichen myxedematosus have a long-term, disfiguring, possibly disabling disorder. The risks and benefits of systemic therapy must be weighed carefully.
-
Grouped, erythematous, flesh-colored, dome-shaped papules are present on the hand and fingers.
-
Low-power photomicrograph of a histopathologic specimen demonstrates the wide separation of the collagen fibers near the large collection of mucin in the dermis.
-
High-power photomicrograph of a histopathologic specimen reveals the large collections of mucin and plump stellate fibroblasts in the dermis.
