Atiphospholipid syndrome (APS) most often leads to thrombotic events, but so then why are some patients with APS bleeding due to it? This post will shed some light on that, as well as the diagnostic criteria for APS.  

APS is a diagnosis made by having either a thrombotic event or a pregnancy loss, plus an associated positive antibody. The three antibodies that can be seen in APS are anti-cardiolipin, anti-beta 2 microglobulin, and lupus anticoagulant. Now what if a patient has a positive antibody test but no thrombotic event/pregnancy loss history? Then it isn’t APS. But what if a patient not only has 1 of those antibodies but rather 2 of them? Still, not APS. Okay but what about all 3 antibodies? Is it APS then? No. 

Okay so let’s say we have a patient that meets criteria for APS. Now, why is a patient with a pathology that leads to increased coagulation at increased risk for bleeding? Well, the most common clinical feature of APS is thrombosis, which shouldn’t surprise anyone. But what is the second most prevalent feature of APS? Thrombocytopenia and hypoprothrombinemia are the main culprits. Now, this thrombocytopenia generally isn’t severe enough to commonly cause hemorrhagic events, but it certainly can. In fact, the 4th leading cause of death in patients with APS at 10 year follow up is hemorrhage. Now it should be pointed out that this number is likely inflated due to the fact that the mainstay treatment of APS is anticoagulation. 

Regardless, it should be noted that just because a patient has APS, does not mean the associated risk of bleeding is minimal. Instead, it is elevated in this patient population.  


Kubisz, P., Holly, P., & Stasko, J. (2022). Bleeding in Patients with Antiphospholipid Antibodies. IntechOpen. doi: 10.5772/intechopen.97856

Erkan D, MD, MPH & Ortel T, MD, PhD. Diagnosis of antiphospholipid syndrome. Post TW, ed. UpToDate. Waltham, MA: UpToDate Inc. (Accessed on August 10, 2023.)

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