Reticular erythematous mucinosis (REM) is a skin condition caused by fibroblasts producing abnormally large amounts of mucopolysaccharides.

[6] Patients with reticular erythematous mucinosis have also been reported to have other conditions like myxedema, hypothyroidism, Hashimoto's thyroiditis, monoclonal gammopathy, and HIV infection.

[7][8] Menstruation, heat, x-ray therapy, oral contraceptives, pregnancy, and perspiration can all induce or worsen reticular erythematous mucinosis.

[11][12] A primarily lymphocytic perifollicular infiltrate may exist,[13] along with a small number of histiocytes, factor XIIIa-positive dendrocytes, and admixed mast cells.

[15] A characteristic of reticular erythematous mucinosis is the separation of dermal collagen bundles, and the upper and mid dermis are the primary areas where variable amounts of basophilic mucin are visible.