Raynaud's phenomenon and vascular disease in systemic sclerosis

Raynaud's phenomenon (RP) is very often the first manifestation of SSc preceding the onset of all the other signs and symptoms of the disease. Two structures are involved in the pathogenesis of RP: the endothelium and the peripheral nervous system (PNS). The hypothesis is that SSc modifies consistently the activity of both these systems leading eventually to RP. The disease, through the injury to the endothelium, jeopardizes the basilar endothelial-dependent vascular tone control. An increase of endothelin, a potent endothelial-derived vasoconstrictor, and the reduction of nitric oxide, one of the main endothelial vasodilators, are two key events involved in the genesis of RP. The PNS is also targeted by the disease as demonstrated by the high incidence of neuropathy in SSc patients. A marked reduction of sensory fibres has been detected in SSc skin. Thus, the involvement of nerve terminals reduces the vasodilatory, endothelial dependent or independent, potential of the neuropeptides released by sensory nerve endings. Indeed, an increased sensitivity of alpha 2 adrenoceptors mediated vasoconstriction has been shown in SSc skin. The complex vasodilatory network formed by the interaction between the endothelium and the PNS seems greatly damaged by SSc leading inesorably toward vascular tone dysfunction clinically evident as RP.