THE ETIOLOGY OF RAYNAUDS-PHENOMENON

The literature on Raynaud's phenomenon (RP) describes a complex and co nfusing picture of abnormalities that has suggested a multifactorial a etiology, Current research suggests that the underlying disorder is re lated to a local fault at the level of the digital microcirculation, I t is likely that many of the biological changes described in RP are se condary manifestations of this primary abnormality, The strong familia l relationship of RP suggests a genetic link although this has not yet been characterized. An overactivity of the sympathetic nervous system appears less likely as a candidate for the primary abnormality and dy sfunction at the level of the nerve, and vessel wall may be more impor tant. Digital cutaneous neurones show a deficient release of the vasod ilatory calcitonin gene related peptide in PR. This may represent a pr imary fault that is confounded by other factors, which are influenced by cold or emotional triggers. Vasoconstricting substances such as cat echolamines, endothelin-1 and 5-hydroxytryptamine, which may all be re leased in response to cold exposure, could cause digital artery closur e and the associated symptoms of RP. In some cases, this would trigger a cascade of neutrophil and platelet activation, which through the re lease of inflammatory mediators, contribute to the endothelial damage seen with more severe RP. It is hypothesised that disturbance to the i ntricate functioning of the endothelium, and secondary compensation at local or systemic level, may appear over time, There is, therefore, s till a need to differentiate the true aetiological factors from those that are causal associations with Raynaud's phenomenon, Progress is sl owly being made with better understanding of the intricacies between t hese factors and the microcirculation, Deepening our comprehension of the 'normal' mechanisms that influence microvascular blood flow is nec essary to develop a better understanding of the pathophysiology of Ray naud's phenomenon. (C) 1998 The International Society for Cardiovascul ar Surgery. Published by Elsevier Science Ltd. All rights reserved.