Antiphospholipid Antibody Syndrome (APS)
antiphospholipid antibody syndrome
Overview
- We show a phospholipid bilayer and antibody attack the phospholipid.
- The immune complex can trigger clot formation (thromboembolism).
- It occurs in isolation or as a part of another autoimmune disease, such as SLE.
Clinical Features
Key features include:
- Deep vein thrombosis (DVT) & Thrombocytopenia
- Livedo racemosa (broken, asymmetrical skin mottling), which is more specific for APS than is livedo reticularis (which is symmetrical skin mottling) and is found in healthy individuals.
- Late-term miscarriages
- Strokes, Microthrombosis, and Organ infarction. There are microthrombotic manifestations in the skin (eg, livedo racemose), as well as large vessel infarction in the brain (strokes) and in the cardiopulmonary, renal, and GI (esp. the liver) organs.
- Migraines are also a common, helpful clue to the disorder.
Laboratory Testing
- In regards to APS testing, we use immunoassays looking for antibodies directly to phospholipids, their binding proteins, or the bound protein-phospholipid complexes.
Anticardiolipin (aCL) & Anti-Beta-2 glycoprotein I (aB2GPI)
- Specifically, we test for antibodies to anticardiolipin (aCL) (a phospholipid antigen) or anti-Beta-2 glycoprotein I (aB2GPI) (a phospholipid binding protein).
Lupus Anticoagulant
- And we use the lupus anticoagulant test (a 3-step functional coagulation assay). Note that the name “anticoagulant” is counterintuitive: a positive test actually indicates a prothrombotic state. Also, although the test indicates APS, less than half of the people who have a positive “lupus” anticoagulant test will end up having lupus, itself.
False Positive RPR or VDRL (Syphilis)
- As well, APS can generate a false positive RPR or VDRL (both tests rely on the same syphilis antigen to diagnose syphilis). At one time, clinicians used the false positive RPR or VDRL to diagnose APS but this is an unreliable approach, so it has fallen out of favor now that immunoassays are readily available.
Treatment Implications
- Identification of APS is important because anticoagulation (rather than simply antiplatelet therapy, alone) is key to trying to prevent thromboembolism in APS.
- As well, it is important that patients with APS use progesterone-only OCPs (rather than estrogen-containing OCPs).