Antiphospholipid syndrome
Description
- Acquired autoimmune thrombophilia: persistent antiphospholipid antibodies + thrombosis or pregnancy morbidity
- *Antibodies alone are not the syndrome* - persistence over >=12 weeks and a clinical event are both required
- Primary (~50%) or secondary to SLE and other CTDs
The three antibodies
- Lupus anticoagulant (LA) - a functional clotting assay, not an antibody measurement
- *Paradox: prolongs the aPTT in vitro but causes thrombosis in vivo*
- Anticardiolipin (aCL) IgG/IgM
- Anti-beta2-glycoprotein I (anti-beta2GPI) IgG/IgM
Clinical manifestations
- Venous thrombosis - DVT, PE (commonest)
- Arterial thrombosis - stroke and TIA in the young, MI, limb ischaemia
- Microvascular - livedo racemosa, livedoid vasculopathy, aPL-nephropathy, pulmonary haemorrhage, adrenal infarction
- Obstetric - recurrent early miscarriage, fetal death, severe pre-eclampsia, placental insufficiency
- Cardiac valve - Libman-Sacks endocarditis, valve thickening
- Haematological - thrombocytopenia, autoimmune haemolytic anaemia
Catastrophic APS (CAPS) - <1%
- >=3 organs involved within 1 week, with histological small-vessel thrombosis, in a patient with aPL
- Mortality ~30-50% even with treatment
- Triggers: infection (most common), surgery, anticoagulant withdrawal, malignancy, pregnancy, SLE flare
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