Fulminant ecchymosis as the initial manifestation of antiphospholipid syndrome (APS) triggered by respiratory syncytial virus (RSV) infection: A case report and review of the literature

Makino, Jun; Koshy, Sanjana; Bajaj, Sonal; Jeong, Young-Gwang; Perlman, David C.

A probable association and a causal relationship between infections and APS have been well reported, and various organisms have been implicated [3] . A "two hit" model has been proposed to explain the pathogenesis of thrombosis of APS [4, 5] . Initially, antiphospholipid (aPL) antibodies bind to endothelial cells and promote overproduction of tissue factor and thromboxane A2. This results in a procoagulant state constituting the-"first hit". The complement cascade is then activated by the aPL antibodies and the complement system leading to damage of the endothelial cells and resulting in thrombosis. This process is often potentiated by the presence of inflammation, estrogen or coagulation-regulatory proteins (protein C, prothrombin, plasmin), -constituting the "second hit". When aPL antibodies bind to endothelial cells in the first step, b2-Glycoprotein Inhibitor (b2-GPI) is usually required as a cofactor to unite aPL antibodies and endothelial cells. In certain infections, the b2-GPI molecule and the infectious agents' epitopes are known to be structurally and sequentially similar, and this molecular similarity is considered a key mechanism of APS associated with infection [6] . Hepatitis C virus (HCV), Epstein-Barr virus (EBV), Varicella virus, Parvovirus B19, Cytomegalovirus (CMV), Human Immunodeficiency virus (HIV), and Adenovirus are some of the viruses associated with APS and circulating anti-b2-GPI [7] . In contrast, Sene and coworkers have suggested that viral infections and some bacterial infections may be associated with positive anticardiolipin antibodies (aCL), but not associated with anti b2-GPI as seen in our case [8] .