Lichen Myxedematosus

Lichen myxedematosus, or papular mucinosis, is characterized by a more or less extensive eruption of asymptomatic, soft papules generally 2 to 3 mm in diameter, associated with a monoclonal gammopathy. Although densely grouped, they usually do not coalesce. The face and arms are the most commonly affected areas . In some instances, in addition to papules, large nodules may be present, especially on the face . Although the disease is very chronic, spontaneous resolution has been reported .

In a variant of lichen myxedematosus called scleromyxedema, a generalized eruption of papules as in lichen myxedematosus and, in addition, diffuse thickening of the skin associated with

erythema are found. There is marked accentuation of the skin folds, particularly on the face. Scleromyxedema can be differentiated from scleroderma clinically by the papular component and the absence of telangiectasias. Transitions of lichen myxedematosus to scleromyxedema do occur. Acral persistent papular mucinosis presents multiple small papular lesions on the hands and forearms . The clinical and histopathologic features resemble the discrete papular form of lichen myxedematosus . The detection of immunoglobulin A (lgA) monoclonal gammopathy in one case also suggests that it is a localized variant of lichen myxedematosus . Cutaneous mucinosis of infancy may also represent a localized form of papular mucinosis on the upper extremities unassociated with monoclonal gammopathy . It may remit spontaneously .

Multiple dome-shaped papules with histopathologic features suggestive of papular mucinosis have been noted in Birt-Hogg-Dube syndrome .

Histopathology.

In lichen myxedematosus, fairly large amounts of mucin are present. In contrast with pretibial myxedema, however, the mucinous infiltration is found only in circumscribed areas, is most pronounced in the upper dermis, and is associated with an increase in fibroblasts and collagen . The collagen bundles may show a rather irregular arrangement.