Circumscribed myxoedema of lichen myxoedematosus as a sign of faulty formation of the proteoglycan macromolecule.

Using a new method devised by our laboratory, the ultrastructure of dermal glycosaminoglycan in an involved area of lichen myxoedematosus was examined. Although histochemical and biochemical studies have indicated simply an accumulated deposition of hyaluronic acid in the lesion, the glycosaminoglycan ultrastructure within it was distinctly different from that in normal skin. The glycosaminoglycan structure of normal skin was similar to the proteoglycan aggregate model described by Rosenberg (1975). As confirmed by the enzymatic digestion procedure, it represents the ultrastructure of hyaluronic acid bound to glycosaminoglycans such as dermatan sulphate or chondroitin sulphate. In contrast, hyaluronic acid filaments observed in lesions of lichen myxoedematosus contained no glycosaminoglycan subunits.