London - Lichen myxedematosus (LM) is not a single disease, but represents two clinicopathologic subsets that are important to distinguish because they differ with respect to prognosis and treatment, said Franco Rongioletti, M.D., at the annual meeting of the European Association of Dermatology and Venereology.
"Lichen myxedematosus is a chronic idiopathic disorder characterized by the appearance of lichenoid papules, nodules and/or plaques that are due to dermal mucin deposition with a variable degree of fibrosis in the absence of thyroid disease. It is often, but incorrectly, considered to be a cutaneous mucinosis that is always associated with systemic disease, whereas, in fact, there is also a localized variant of LM characterized by skin involvement with no systemic findings," explains Dr. Rongioletti, professor of dermatology, University of Genoa, Italy.
"The generalized and sclerodermoid form, best known as scleromyxedema, runs a course that is chronic, progressive, disabling and sometimes even fatal, and treatment with chemotherapeutic and immunomodulating agents may be indicated to manage the systemic disease. However, these potentially toxic medications should not be prescribed for patients with localized LM who instead may be appropriately managed with a wait-and-see approach or a topical treatment. Sometimes, there is a spontaneous healing of skin lesions."
"It may be, however, that the prevalence of localized LM is underestimated," he says.
The eruption associated with the generalized form of LM is usually widespread, tends to involve the hands, forearms, face, neck, upper trunk and thighs, and the histology reveals mucin deposition with fibroblast proliferation and fibrosis. In contrast, the lesions in patients with the localized form of LM are usually seen only on the upper and lower limbs and trunk, and the presence of fibroblast proliferation on biopsy is more variable.
A small proportion of patients with generalized LM will have neurological and rheumatological findings. Monoclonal gammopathy is the most common systemic disorder, occurring in more than 80 percent of patients with generalized LM. In the United States, melphalan is usually prescribed as the treatment of choice for managing the plasma cell dyscrasia, Dr. Rongioletti says.
"This alkylating agent can result in some clinical improvement, but it also appears to be an important cause of death in patients with generalized LM because of its potential to induce hematologic malignancies and septic complications," he notes.
Alternative chemotherapeutic agents that have been used in patients with generalized LM include cyclophosphamide, methotrexate, chlorambucil and 2-chlorodesoxyadenosine. The effects of systemic corticosteroids are variable but even when the response is good, the benefit is temporary.
Interventions that appear to be promising but require further study include high-dose intravenous immunoglobulins, autologous stem cell transplantation and thalidomide.
In addition to the importance of clinically distinguishing the localized and generalized forms of LM, Dr. Rongioletti notes attention should be paid to using the correct nomenclature.
"Lichen myxedematosus, papular mucinosis and scleromyxedema are terms that have often been used interchangeably. While lichen myxedematosus and papular mucinosis are proper synonyms, scleromyxedema should be used only when referring to the generalized, sclerodermoid form of LM," he says.
Dr. Rongioletti also discussed a new finding regarding a potential prognostic indicator for cardio-cutaneous mucinosis as well as Adenopathy and Extensive Skin Patch Overlying a Plasmacytoma (AESOP) syndrome, a recently described cutaneous mucinoses.
He notes that primary mitral valve prolapse (MVP), a relatively common finding that affects up to 5 percent of the general population, is associated with a myxomatous degeneration of the mitral valve leaflets. Although the condition is generally asymptomatic, there is a small subset of affected patients who seem to be at increased risk for complications, including arrhythmias and sudden, unexpected death.
"These events are thought probably to be related to the myxomatous degeneration of the mitral valve," Dr. Rongioletti observes.