[Livedo: from pathophysiology to diagnosis].
OBJECTIVE
We propose a diagnostic approach when facing a livedo. First, the pathophysiology of the livedo is reviewed using key articles barely quoted in the literature. Then the topic is handled in two ways. Figures and tables allow a rapid reading convenient "at the patient's bedside". The subject is also reviewed thoroughly, and we emphasize the intricacy of the various pathophysiological mechanisms involved for each livedo's related disease. Diseases associated with livedo are then briefly described with emphasis on the key diagnostic features and prevalence. Usefulness of the main diagnostic procedures is discussed.


BACKGROUND
A livedo is a usually purplish-blue erythema, reticulated (small and complete meshes) or racemosa (large broken circular segments) which is related to a slowdown of the blood flow in the dermic venules. These venules form adjacent circles communicating with each other, parallel to the skin surface. The blood flow slowdown may be due to a local vasoconstriction (vasomotor livedo) or to an arteriolar occlusion. Arteriolar occlusion may be related to blood abnormalities (thrombosis, high viscosity, embolus) or to increased parietal thickness (vasculitis, calcic deposition, intimal hyperplasia). It is not always possible to clinically distinguish a vasomotor livedo from those associated with diseases. Diagnostic procedures should be oriented by the medical history, the features of the livedo, and associated symptoms. Usefulness of the skin biopsy is usually limited to the situations where the livedo is infiltrated or necrotic.


CONCLUSIONS
To raise controversy about their importance and implications, some pathophysiological data are presented: intimal pseudohyperplasia in Sneddon's syndrome and antiphospholipid syndrome, and white cell activation in essential thrombocythemia.
Duval
A
A
Service de médecine interne de l'hôpital Saint-Louis, 1, avenue Claude-Vellefaux, 75010 Paris, France. arnaudduval@netcourrier.com
Pouchot
J
J
D003937:Diagnosis, Differential; D006801:Humans; D054068:Livedo Reticularis / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D008833:Microcirculation / Q000473:pathology; D012867:Skin / Q000473:pathology