Cutaneous Mucinoses

Abstract

Abstract Cutaneous mucinoses are a heterogeneous group of diseases whose main characteristic is the abnormal excessive deposition of mucin (glycosaminoglycans) in the skin. The aetiopathogenesis of cutaneous mucinoses is unknown, although a few cytokines such as tumour necrosis factor α and β, interleukin 1, interleukin 6, and transforming growth factor β and/or polyclonal immunoglobulins and monoclonal and other unidentified factors in patient serum, may induce pathological stimulation of glycosaminoglycan synthesis. Cutaneous mucinoses are divided into two groups: primary cutaneous mucinoses in which mucin deposition is the main histological feature leading to specific clinical lesions, and secondary mucinoses in which mucin deposition is only an additional histological epiphenomenon. Primary mucinoses can be divided into dermal and follicular mucinoses. The former includes lichen myxoedematosus (papular mucinosis), divided into diffuse/generalised lichen myxoedematosus (also called scleromyxoedema) and the localised form, reticular erythematous mucinosis (REM), scleroedema, mucinosis in thyroid disease, papular and nodular mucinosis in connective tissue diseases, self‐healing (juvenile) cutaneous mucinosis, cutaneous focal mucinosis and digital myxoid cyst. While the follicular mucinoses include Pinkus follicular mucinosis and urticaria‐like follicular mucinosis. Associated disorders include paraproteinaemia (scleromyxoedema, scleroedema), diabetes mellitus (scleroedema), hyperthyroidism (pretibial myxoedema), hypothyroidism (generalised myxoedema), and lupus erythematosus, dermatomyositis or scleroderma (papular and nodular mucinosis in patients with connective tissue). There are no evidence‐based therapies for the main conditions, although some positive results have been obtained with intravenous immunoglobulin in scleromixoedema, antimalarials in REM and phototherapy in scleroedema.