14 - Cutaneous mucinoses

Abstract

The mucinoses represent a diverse group of disorders that have in common the deposition of basophilic, finely granular, stringy material (mucin) in the connective tissues of the dermis, in the pilosebaceous follicles (follicular mucinoses), or in the epidermis and tumors derived therefrom (epithelial mucinoses). The most important mucinoses are the dermal ones where glycosaminoglycans (GAGs), also known as acid mucopolysaccharides, accumulate in the dermis. Hyaluronan, in contrast to the other GAGs, is non-sulfated and is synthesized on the inner face of the plasma membrane of the fibroblast. Fragmentation of the dermal collagen is quite common in the dermal mucinoses. In many of the mucinoses, there appears to be an increased production of acid mucopolysaccharides by fibroblasts, although in myxedema it has been suggested that impaired degradation leads to accumulation of dermal mucin. In the mucopolysaccharidoses, the predominant dermal mucin is chondroitin sulfate, rather than hyaluronan. The two most common stains for demonstrating mucin in the skin are Alcian blue and colloidal iron. Metachromasia of mucin is usually demonstrated with the toluidine blue or Giemsa methods.