Ultrastructural characteristics of the skin in a form of the Ehlers-Danlos syndrome type IV. Storage in the rough endoplasmic reticulum.

The ultrastructural study of an individual with one form of the Ehlers-Danlos syndrome type IV has shown abnormalities in dermal connective tissue architecture and fibroblast morphology. Skin thickness was reduced to about 25 per cent that of the normal, and collagen fibrils and fiber bundles were significantly smaller in diameter than those from an age-, sex-, and site-matched control. In all fibroblasts of the dermis and other connective tissues, the rough endoplasmic reticulum was grossly dialted and dominated the cytoplasm. Dilation may result from storage of an abnormal type III collagen molecule which is stored in these cells in culture. Accordingly, normal type III collagen in skin is markedly reduced. The observed alterations in collagen fibril morphology and dermal organization may be a consequence of an atypical ratio of type I and III collagen in the dermal matrix. Although smooth muscle and endothelial cells have the ability to synthesize and secrete type III collagen, they showed no unusual distension of the rough endoplasmic reticulum in skin, synthesizing different gene products, or different processing mechanisms for the same gene product by different cell types.