Antiphospholipid Antibody Syndrome Risk Factors

Demographic and Clinical Risk Factors

Young adults under 50 years of age have the strongest association between antiphospholipid antibodies and thrombotic events, particularly stroke, with 9.7% of ischemic stroke patients having demonstrable anticardiolipin antibodies compared to 4.3% of controls 1, 2
Systemic lupus erythematosus is the most significant associated condition, with APL antibody prevalence being higher in patients with lupus 1
In children, antiphospholipid antibody syndrome may be suspected in those with recurrent deep vein thrombosis, recurrent pulmonary emboli, or thrombotic events occurring during childhood or adolescence 3

Inherited thrombophilias including Factor V Leiden, prothrombin G20210A mutation, and MTHFR C677T polymorphism increase risk, with associations stronger in young patients (<55 years) 1, 2
The prothrombin G20210A mutation has an odds ratio of 1.32 (95% CI, 1.03 to 1.69) for stroke, with stronger associations in the young 2
The MTHFR C677T polymorphism, associated with high homocysteine levels, has an OR of 1.26 (95% CI, 1.14 to 1.40) for stroke in homozygous mutation carriers 1
A family history of thrombotic events is a key risk factor that should prompt evaluation for prothrombotic states 3

Patients with both lupus anticoagulant and anticardiolipin antibodies had a higher event rate (31.7%) compared to patients negative for both antibodies (24.0%) 1
Medium to high antibody titers carry significantly greater risk than low-titer antibodies, which may not confer the same thrombotic risk 4

Coexisting prothrombotic conditions including protein C, protein S, or antithrombin III deficiencies increase risk when combined with APL antibodies 1, 2
The likelihood of stroke from prothrombotic states increases substantially when occurring in children with other risk factors 3
Recurrent pregnancy loss (≥3 consecutive losses before 10 weeks gestation) or unexplained fetal loss at ≥10 weeks gestation are major risk factors for obstetric APS 5, 6
Delivery before 34 weeks due to preeclampsia or placental insufficiency with growth restriction also indicates increased risk 5

The elderly population presents conflicting data regarding the association between APL antibodies and stroke recurrence, with APL antibody prevalence being higher in elderly patients but with less clear thrombotic risk stratification 1