Raynaud's phenomenon and systemic sclerosis.

In systemic sclerosis, the exaggerated generalized vasospastic tendency is clinically represented by Raynaud's phenomenon as shown by an early digital arterial closure after cold stimulation, and by an inadequate vasodilatory response to heat. The phenomenon is not restricted to the extremities, and can also occur in internal organs. Repeated attacks of Raynaud's phenomenon may contribute to vascular disease in systemic sclerosis by a mechanism of reperfusion injury of the endothelium, and may contribute to tissue fibrosis. Although the aetiology and pathogenesis of Raynaud's phenomenon remain unknown, recent advances in the understanding of mechanisms of vascular tone control provide us with an opportunity to reconsider the pathogenetic process of Raynaud's phenomenon. It is now clear that neuropeptides, the vascular endothelium, and platelets are the three major contributors to the control of vascular tone. Our hypothesis suggests the presence of a sensory nervous system failure, leading to an unopposed endothelial and platelet control of vascular tone. Endothelial injury and platelet activation in systemic sclerosis lead to a shift in vascular function to a pro-vasospastic function not balanced by a vasodilatory sensory input; thus, enhanced vasospasm is generated. The investigation of the role of local vascular mediators in vasospasm may lead to a better understanding of vascular tone control and of Raynaud's phenomenon pathophysiology in systemic sclerosis.