Autoimmune hypercoagulable disorder (primary or SLE-associated) marked by recurrent venous/arterial thromboses and pregnancy complications due to antiphospholipid antibodies.
Major cause of thrombosis and recurrent pregnancy loss in young patients, especially women. Recognizing APS allows life-saving anticoagulation and high-risk pregnancy management; classic lab findings and lupus association appear frequently on exams.
Young woman with recurrent miscarriages (≥2 first-trimester losses or ≥1 later loss) often with a history of unprovoked DVT/PE.
Unprovoked DVT or stroke in a patient under 50, especially if they have autoimmune features (e.g., SLE) or a mottled rash (livedo reticularis).
Labs: can show a paradoxical prolonged PTT despite clotting and a false-positive VDRL syphilis test (due to anticardiolipin antibody).
Suspect APS in young patients with unexplained clot or multiple pregnancy losses; order antiphospholipid antibody testing.
If initial tests (anticardiolipin, anti-β2 GP1, lupus anticoagulant) are positive, repeat after ≥12 weeks to confirm persistence (required for diagnosis).
Exclude other causes of hypercoagulability (e.g., inherited thrombophilia, malignancy) and address any triggers (smoking, OCP use).
For confirmed APS, start long-term anticoagulation (warfarin for thrombosis; LMWH+aspirin if pregnant) and screen for underlying SLE (ANA testing).
primary APS vs SLE: lupus has multisystem features (rash, arthritis, nephritis) and other antibodies in addition to aPL.
Inherited thrombophilia
e.g., Factor V Leiden; genetic hypercoagulability causing clots but no autoimmune antibodies or pregnancy losses.
Heparin-induced thrombocytopenia
hospitalized patient on heparin with new thrombosis & low platelets (antibody to PF4-heparin, not chronic APS).
Long-term anticoagulation (typically warfarin, INR 2–3) is indicated after a thrombotic event to prevent recurrence (avoid DOACs in high-risk APS).
In pregnancy, avoid warfarin (teratogenic) and use LMWH + low-dose aspirin throughout pregnancy to prevent miscarriage/preeclampsia.
Manage risk factors: no smoking, avoid estrogen-containing OCPs, control BP and lipids. If no thrombosis but high-risk antibody profile, consider prophylactic aspirin.
Lupus anticoagulant causes a prolonged PTT in vitro but a hypercoagulable state in vivo (paradoxical lab finding).
Anticardiolipin antibodies can yield a false-positive VDRL/RPR syphilis test.
Unexplained clot at young age or ≥3 pregnancy losses → always evaluate for APS; missing it risks preventable strokes or stillbirths.
Catastrophic APS: rapid, diffuse thromboses causing multi-organ failure (high mortality) – requires ICU care with IV heparin, high-dose steroids, and often plasmapheresis/IVIG.
Unprovoked thrombosis or recurrent miscarriage → suspect APS.
Order aPL panel: lupus anticoagulant (e.g., dRVVT), anticardiolipin (IgG/IgM), anti-β2 glycoprotein I.
If any aPL test is positive → repeat the same test in ≥12 weeks to confirm persistence (needed for APS diagnosis).
If clinical criteria (clot or pregnancy morbidity) + persistent antibodies met → diagnose APS. Check for underlying SLE (ANA) if not already known.
Treat with lifelong anticoagulation (warfarin; or LMWH+ASA if pregnancy). Refer to high-risk OB for pregnant APS patients; monitor and manage cardiovascular risks.
Young woman with ≥3 miscarriages and a prior DVT, now with a swollen leg; labs show prolonged PTT and positive anticardiolipin → antiphospholipid syndrome.
25‑year‑old with SLE develops stroke symptoms; testing reveals lupus anticoagulant and anticardiolipin antibodies → secondary APS causing arterial thrombosis.
Case 1
A 32‑year‑old woman with three first‑trimester miscarriages and a prior unprovoked DVT presents with a swollen, painful left leg.
Case 2
A 25‑year‑old woman with long-standing SLE develops sudden slurred speech and right-arm weakness.
Clot formation and livedo reticularis in antiphospholipid syndrome (illustration).
