Lichen myxedematosus (LM) is a localized primary dermal mucinosis. There are 4 subtypes of this localized variant:

1. A discrete papular form
2. Acral persistent papular mucinosis
3. Cutaneous mucinosis of infancy
4. A pure nodular form

All subtypes with the exception of cutaneous mucinosis of infancy are typically observed in adults. Although the pathophysiology is not understood, LM can be observed in association with human immunodeficiency virus (HIV) infection, hepatitis C infection, and, historically, exposure to toxic oil or L-tryptophan.

Clinical features of LM vary based on the subtype. Discrete papular LM is characterized by the presence of 2- to 5-mm papules on the trunk and extremities. Unlike scleromyxedema, the face is typically spared and induration is not observed. In acral persistent papular mucinosis, patients present with papules on the dorsal hands and extensor forearms. In cutaneous mucinosis of infancy, patients present with papules or plaques on the neck, elbows, and trunk. Nodular LM is characterized by the development of multiple nodules on the trunk and extremities. In these localized variants, progression to scleromyxedema does not occur. While lesions tend to progress slowly, there is no systemic involvement.

In contrast to scleromyxedema, the criteria for the diagnosis of localized LM includes papular or nodular lesions or plaques, mucin deposition with or without fibroblast proliferation, absence of thyroid disease, and absence of monoclonal gammopathy.