Ultrastructural changes in scleromyxedema.

Skin biopsy specimens from a 60-year-old patient with paraproteinemia and generalized changes of the skin typical of scleromyxedema were studied with the electron microscope. The dermis was dominated by collagen fibrils and accumulations of peculiar connective tissue cells, while elastic tissue was sparse and in some areas completely absent. Large, sharply demarcated areas of a filamentous material were occasionally observed. The collagen fibrils were often surrounded by thin filaments with a periodic segmentation and by many glycosaminoglycan (mucopolysaccharide) filaments. The elastic fibres contained large amounts of elastic fibrils and small amounts of a homogenous matrix. The cytoplasm of the above-mentioned cells was dominated by lysosomes in different stages of development, often occupying almost all the cytoplasmic area. The collagen fibrils were found in close relation to these cells, frequently inside invaginations of the cells. Furthermore, collagen fibrils were observed free in the cytoplasmic area and inside the lysosomes, indicating lysosomal degradation of collagen.