Background: A scleroderma-like genetic disease, congenital fascial dystrophy, probably a variant of stiff skin syndrome described by Esterly and McKusick, was found to be related to genetically determined fascial abnormalities. Our previous electronmicroscopic study disclosed as a main pathologic finding presence of giant amianthoid-like collagen fibrils in the affected fascia. Objective: The aim of the present study was to disclose the collagen abnormalities in the affected and control fascias and in the patient's fibroblast cultures derived from the skin and fascia. Methods: The study was performed by histologic, immunohistochemical, and electronmicroscopic techniques. Immunohistochemical studies were done with the use of monoclonal antibodies: anti-collagens I, III, IV, and VI, anti-laminin, anti-fibronectin, anti-desmin, anti-spectrin, anti-vimentin, anti-laminin, anti-heparan sulfate, and anti-alpha-actinin. Electronmicroscopic studies were performed on the fascia sections and on cultured fibroblasts. Results: The main abnormality leading to giant collagen fibril formation was presence of myofibroblasts, absence of collagen III, and overproduction of spectrin and collagen type VI, mainly its filamentous form. Conclusion: Our findings suggest that the abnormal composition of the fascia could depend on modulation of fibroblasts into myofibroblasts capable of producing spectrin and long-spacing collagen. (J Am Acad Dermatol 2000;43:797-802.)