Updated classification of papular mucinosis, lichen myxedematosus, and scleromyxedema

Lichen myxedematosus (LM) is an idiopathic cutaneous mucinosis; its classif ication dates back to 1953, when Montgomery and Underwood distinguished 4 t ypes of LM: a generalized lichenoid eruption, later called scleromyxedema, a discrete papular from, a localized or generalized lichenoid plaque form, and an urticarial plaque form. In the literature, the terms LM, papular muc inosis, and scleromyxedema have been often used indiscriminately as synonym s, but most reported cases of LM or papular mucinosis without indication of the subtype appear in fact to be cases of scleromyxedema. On the basis of personal experience, the anatomoclinical manifestations of published cases of LM, papular mucinosis, and scleromyxedema are reviewed to distinguish cl early between a generalized form with systemic, even lethal, manifestations and a localized form, which does not run a disabling course. LM includes t wo clinicopathologic subsets: a generalized papular and sclerodermoid form (also called scleromyxedema) and a localized papular form. Diagnosis of scl eromyxedema should fulfill the following criteria: (1) generalized papular and sclerodermoid eruption; (2) mucin deposition, fibroblast proliferation, and fibrosis; (3) monoclonal gammopathy; and (4) the absence of thyroid di sease. The criteria for localized LM are as follows: (1) papular or nodular /plaque eruption; (2) mucin deposition with variable fibroblast proliferati on; and (3) the absence of both monoclonal gammopathy and thyroid disease. The localized form is subdivided into 5 subtypes: (1) a discrete papular fo rm involving any site; (2) acral persistent papular mucinosis involving onl y the extensor surface of the hands and wrists; (3) self-healing papular mu cinosis, of a juvenile and an adult type; (4) papular mucinosis of infancy, 3 pediatric variant of the discrete form or of acral Persistent papular mu cinosis; and (5) nodular form. A third group of atypical or intermediate fo rms, not meeting the criteria for either scleromyxedema or the localized fo rm, includes cases of (1) scleromyxedema. without monoclonal gammopathy (2) localized forms with monoclonal gammopathy and/or systemic symptoms, (3) l ocalized forms with mixed features of the 5 subtypes, and (4) not well-spec ified cases.