Increased capillary permeability in systemic sclerosis: help or hindrance?

Accepted for publication 14 March 1996. Systemic sclerosis (SSc) is a connective tissue disease characterised by an increased secretion of normal extracellular matrix proteins in mesenchymal tissue, and by widespread morphofunctional capillary abnormalities.' 2 Most of the clinical features of SSc are clearly related to vascular lesions; moreover, a diffuse microangiopathy is a prominent feature in all tissues, regardless of any overt clinical involvement." Diffuse endothelial damage caused by a cytotoxic factor could be the initial lesion67: such damage has been clearly demonstrated by ultrastructural studies8 and by the finding of increased plasma von Willebrand's activity, factor VIIVvon Willebrand's factor antigen,9 and tissue plasminogen activator'0 in patients with SSc. Distinctive microvascular changes in SSc include: dilated and distorted capillary loops," diminished capillary density often culminating in regional avascularity," prolonged phases ofreduced or ceased capillary perfusion as a result of cold induced peripheral vasospasm, and partial occlusion of the capillary lumen by platelet aggregates."-'5 Moreover, it has been well documented that capillary permeability to small solutes such as sodium fluorescein is increased and more rapid