*Antiphospholipid Syndrome - Recent Advances in Clinical and Basic Aspects*


**Table 2.**

*Cumulative clinical features during the evolution of the disease in 1000 patients with APS (adapted [14]).*


#### **Table 3.**

anticoagulation.

*Preliminary criteria for the classification of catastrophic antiphospholipid syndrome (CAPS) [18, 19].*

antibodies now thought to be important in stroke risk, accepted low positive titers and many looked at only one-time point, hence it is difficult to apply the results of those studies [16]. While the purpose of the criteria was to help choose patients for clinical trials, it is the best available tool to avoid over-diagnosis of APS in clinical practice [17].

CAPS is a rare and potentially fatal complication of APS. As described in **Table 3**, the clinical presentation is characterized by acute multi-organ failure due to thromboses of three or more organs within 1 week, associated with the presence of aPL and thrombocytopenia [16]. CAPS can be seen as the first presentation of APS or can be triggered by infection, surgery, or trauma in patients with known APS [19].

In the setting of pregnancy, Obstetric APS (OAPS) is diagnosed if at least one of the clinical criteria and one of the laboratory criteria are met as outlined in **Table 4** [1, 20].

#### **2.2 Ischemic stroke**

Although up to 5% of the population might be positive for aPL antibodies, only a small fraction is diagnosed with APS as per the mentioned criteria [21]. Based on the analysis of 120 full-text papers, the overall estimated aPL frequency in stroke


#### **Table 4.**

*Obstetric APS (OAPS) is diagnosed if at least one of the clinical criteria and one of the laboratory criteria are met [1, 20].*

patients of all ages is 13.5% [22]. Sciascia et al. [7], in a systematic review of data from 5217 patients concluded that the overall aPL frequency was estimated as 17.2% for stroke and 11.7% for the transient ischemic attack, and the presence of aPL seems to confer a five-fold higher risk for stroke or TIA when compared with controls. The cumulative prevalence in the Euro-Phospholipid Project Study was 19.8% for stroke and 11.1% for TIA [14], making it the most common and severe arterial complication of APS.

Notably, it has been suggested that more than 20% of strokes in patients younger than 45 years are associated with APS [23], although this estimate may be inflated by referral bias [24]. The presence and magnitude of the ischemic stroke risk associated with aPL in the older population are more evenly split between finding an increased risk and no increased risk. This suggests that aPL may be a more important stroke mechanism in young people whereas, in older populations, other stroke risk factors take on a greater importance.

aPL associated strokes pose a higher risk for women. The Framingham cohort and offspring study found an increased risk of strokes and TIAs for women with high anticardiolipin but not in men [25]. In another study of 34 women under 45 years of age with ischemic strokes and no traditional vascular risk factors, 35% were found to have anticardiolipin antibodies [26].

Another study demonstrated that high serum concentrations of aPL, regardless of other cardiovascular risk factors, were an important predictor of the risk of future stroke and TIA in only females [27]. The presence of anti-β2GP1 antibodies in young women may increase the stroke risk 2.3-fold according to the RATIO study [28].

In terms of traditional vascular risk factors in APS patients, it is debated whether these or the circulating aPL antibodies are responsible for the accelerated atherosclerosis seen in APS. Hypertension is more prevalent in SLE and APS than in the general population. A study showed that hypertension was the only independent risk factor for arterial manifestations, mainly stroke, in APS [29]. The risk of stroke for LA-positive patients was two-fold in smokers and six-fold in smokers receiving oral contraceptives [25]. The Italian Project on Stroke in Young Adults, a prospective study of 1867 patients showed that family history of strokes, migraines with auras, aPL, discontinuation of antiplatelet or antihypertensive medications and increase in at least one traditional vascular risk factor were independent predictors for thromboembolic events [30]. Overall, this emphasizes the importance of aggressively treating all modifiable stroke risk factors like hypertension, diabetes,


**Table 5.**

*Key factors warranting evaluation of antiphospholipid syndrome.*

hypercholesterolemia, obesity, OCP use, and tobacco use to reduce additional thrombotic risks.

A summary of factors that warrant an evaluation of APS in stroke patients is listed in **Table 5**.

Stroke subtypes in APS may be either thrombotic or cardioembolic depending on the location and size of the occluded vessel [31]. Intracranial stem or branch arterial occlusions and stenosis were reported in 50% of APS patients with stroke [32]. Narrowing of multiple intracranial arteries may occur in APS and indicates vasculopathy rather than vasculitis. Occasionally, there is involvement of the extracranial carotid artery. In a small case series of 17 patients, 32% had extracranial arterial abnormalities [33]. Cardioembolic strokes in APS are associated with left cardiac valvular abnormalities, including irregular thickening of leaflets, nonbacterial vegetations, and valve dysfunction [32]. Stroke subtypes in APS can also vary according to the types of antibodies [34]. Saidi et al. [35], in an analysis of 208 patients with their first stroke, reported that antiphosphatidylserine IgG was associated with cardioembolic strokes, lupus anticoagulant with lacunar strokes, and anticardiolipin IgG and IgM with lacunar, atherosclerotic and cardioembolic strokes. The severity of the thromboembolic event does not relate to the aPL antibody titer.

The type of antibodies present also appears to have an association with increased thrombotic risk. The presence of antiphosphatidylserine antibodies had the highest risk for clinical manifestations of APS, and IgG antiphosphatidylserine antibodies correlated strongly with the presence of lupus anticoagulant. The presence of antiphosphatidylserine antibodies (IgG or IgM) or anti-b2GP-1 (IgG, IgM, or IgA) antibodies improved the specificity for APS over anticardiolipin antibodies alone [36]. In another study, the positive predictive value for antiphosphatidylserine and anti-b2GP-1 antibodies was stronger for arterial thromboses than for venous thromboses [37]. Another study of pregnant women with APS reported that patients with triple aPL positivity (LA, aCL, and anti-B2GPI) and/or previous thromboembolism had an increased likelihood of poor neonatal outcomes than patients with double or single aPL positivity and no thrombosis history [38].

The recurrent risk of stroke in APS patients has been less widely studied as compared to other types of thromboses. Pezzini et al. calculated a cumulative risk of 14% for brain ischemia at 10 years [30]. Recurrent strokes and other thromboembolic events in patients with aPL antibodies have been reported both early (within the first year of an index stroke event) and late (5–10 years) [39]. The initial type of thromboembolic event (i.e. arterial, venous, miscarriage) appears to be the most likely type of event to recur in a given patient according to some studies [40]. The Euro-Phospholipid Project Group reported thrombotic events in 16.6% of patients in the first 5 years of follow-up and in 14.4% in the second 5-year follow-up period.

