The mystery of Sneddon syndrome: relationship with antiphospholipid syndrome and systemic lupus erythematosus.

Since its description in 1965, Sneddon syndrome (SNS) is usually characterized by the association of an ischemic cerebrovascular disease and a widespread livedo reticularis. The presence of many other manifestations suggests that it is a systemic syndrome. The prevalence of anti-phospholipid antibodies (aPL) is highly variable, 41% in our experience. Comparison of patients with or without aPL showed that the fishnet of the livedo was clearly larger in aPL-negative patients who nevertheless, did not develop thrombocytopenia. Seizures and clinically audible mitral regurgitation were more frequently observed in aPL-positive patients. These data lead to consider that SNS is not a unique entity. As patients with primary anti-phospholipid syndrome (APS) and SNS did not differ from those with livedo reticularis, ischemic cerebral events and APS within systemic lupus erythematosus (SLE), there is no reason today to exclude patients with SLE. On one hand, SNS might cover a continuum spectrum joining diverse clinico-biological entities ranging from aPL-negative to SLE-related cases, with primary APS-SNS standing amidst. On the other hand, one might speculate that SNS should be regarded as a nearly similar clinical expression of two distinct disorders, i.e. a peculiar form of APS characterized by preferential arteriolar involvement or on the opposite a primary non-aPL related small artery disease mainly involving brain and skin vessels.