Severe thrombocytopenia (PLT <50×10⁹/L) was associated with arterial thrombotic manifestations in antiphospholipid syndrome, particularly cerebral infarction, at both baseline and during 48-month follow-up.
Key Findings
Results
Severe thrombocytopenia (PLT <50×10⁹/L) was associated with a higher frequency of arterial thrombosis at baseline compared to other platelet count groups.
66.7% of patients with PLT <50×10⁹/L had arterial thrombosis at baseline
62.7% of patients with PLT <50×10⁹/L had cerebral infarction at baseline
Venous thrombosis was most frequent in the PLT 50-<100×10⁹/L group (68.4%)
Analysis was conducted in a two-center baseline cohort of 313 patients with APS, with multivariable logistic regression applied to 300 patients with primary APS or SLE-associated APS
Results
After multivariable adjustment, PLT <50×10⁹/L remained independently associated with higher prevalence of arterial thrombosis at baseline.
Adjusted odds ratio for arterial thrombosis: aOR 2.16 (95% CI 1.07–4.35, P = 0.032)
Adjusted odds ratio for cerebral infarction: aOR 2.37 (95% CI 1.18–4.73, P = 0.015)
Associations were assessed using multivariable logistic regression controlling for potential confounders
The reference group was PLT ≥100×10⁹/L
Results
During 48-month follow-up, PLT <50×10⁹/L was associated with increased risk of any thrombotic event.
Hazard ratio for any thrombotic event: HR 3.28 (95% CI 1.54–6.97, P = 0.002)
Follow-up cohort consisted of 254 patients from the Renji center
Kaplan-Meier curves and Cox proportional hazards models were used to evaluate thrombotic events
Follow-up duration was 48 months
Results
During follow-up, PLT <50×10⁹/L was specifically associated with increased risk of arterial thrombotic events and cerebral infarction, but not venous-related events.
Hazard ratio for arterial thrombotic event: HR 3.95 (95% CI 1.39–11.21, P = 0.010)
Hazard ratio for cerebral infarction: HR 4.11 (95% CI 1.44–11.73, P = 0.008)
No statistically significant association was found between PLT <50×10⁹/L and venous-related thrombotic events
These findings were evaluated in the Renji follow-up cohort (n = 254) over 48 months
Results
Thrombocytopenia in APS showed a differential pattern of thrombotic associations depending on severity, with moderate thrombocytopenia (PLT 50-<100×10⁹/L) most associated with venous thrombosis.
Venous thrombosis was most frequent in the PLT 50-<100×10⁹/L group at 68.4%
Arterial thrombosis predominated in the PLT <50×10⁹/L group at 66.7%
The study categorized baseline platelet count into three groups: PLT <50×10⁹/L, PLT 50-<100×10⁹/L, and PLT ≥100×10⁹/L
This pattern suggests that the severity of thrombocytopenia may differentially influence the type of thrombotic manifestation in APS
Discussion
The authors interpret PLT <50×10⁹/L as potentially providing additional clinical risk information while also possibly reflecting cumulative disease burden and overall APS severity.
The authors note that thrombocytopenia in APS is often regarded primarily as a bleeding-related manifestation
The study suggests the relationship between platelet-count severity and thrombotic manifestations had previously been uncertain
Authors conclude that PLT <50×10⁹/L 'may provide additional clinical risk information but may also reflect cumulative disease burden and overall APS severity'
The study design was a two-center cohort study using both cross-sectional baseline analysis and longitudinal follow-up
What This Means
Antiphospholipid syndrome (APS) is an autoimmune condition that causes the immune system to mistakenly attack proteins that help blood clot, leading to an increased risk of dangerous blood clots. Many people with APS also have low platelet counts (thrombocytopenia), which are the blood cells that help stop bleeding. Low platelets are typically associated with bleeding risk, but this study investigated whether the degree of platelet reduction might also be linked to blood clot formation — specifically arterial clots, which block arteries and can cause strokes.
This research suggests that patients with APS who have severely low platelet counts (below 50×10⁹/L, which is roughly half the lower limit of the normal range) are more likely to have arterial blood clots, and particularly strokes (cerebral infarction), compared to patients with higher platelet counts. This association held up even after accounting for other factors that might explain the difference. Notably, moderately low platelet counts (50–100×10⁹/L) were more associated with venous clots (clots in veins), suggesting that different degrees of thrombocytopenia may relate to different types of clotting problems. Over a 4-year follow-up period, patients with severely low platelets had more than three times the risk of experiencing any thrombotic event and about four times the risk of stroke.
This research matters because it challenges the conventional view that low platelets in APS patients are simply a bleeding concern. Instead, severely low platelets may actually signal a higher risk for dangerous arterial clots, including stroke. This finding could help doctors identify APS patients who need more careful monitoring or more aggressive preventive treatment, though the authors caution that the low platelet count may also simply be a marker of more severe overall disease rather than a direct cause of the increased clotting risk.
Kong J, Su Y, Zhu X, Zhao J, Chen H, Chen X, et al.. (2026). Severe thrombocytopenia is associated with arterial thrombotic manifestations in antiphospholipid syndrome: a two-center cohort study.. Frontiers in immunology. https://doi.org/10.3389/fimmu.2026.1927065