Immune thrombocytopenia (ITP) could be an independent and long-lasting clinical phenotype of Antiphospholipid Syndrome (APS) without other high-risk factors for thrombosis, a new study published in Rheumatology and Therapy revealed.

The study found that positive antiphospholipid antibodies (aPLs) carriers with thrombocytopenia share similar symptoms as patients with primary APS; however, they experience fewer thrombotic risk factors and hardly develop thrombotic events, the study authors noted.

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Prior research has shown that 30% of patients with ITP have aPLs at diagnosis, but most do not develop thrombosis like those with APS. There is controversy surrounding the association between ITP and thrombosis, the researchers noted. A recent study found that the incidence rate of thrombosis in ITP patients is low, although those with positive aPLs tend to have a higher risk, they added.

Thrombocytopenia is a common feature of APS, but some patients with persistent positive aPLs do not develop thrombosis over a long follow-up period. This subgroup of patients may represent a unique clinical phenotype of APS, the investigators noted. Previous studies have shown that smoking, hypertension, and elevated homocysteine levels can increase the risk of thrombotic events, particularly arterial thrombosis. Additionally, APLs and hyperhomocysteinemia are associated with an increased venous and arterial thrombosis risk, they continued.

The study compared the characteristics of patients with persistent positive aPLs with patients with primary APS with thrombocytopenia. One hundred two patients were enrolled, including 47 thrombocytopenic patients with continuous positive aPLs and 55 patients with diagnosed primary APS. The inclusion criteria were based on the 2006 Sydney classification criteria, requiring confirmed positive aPLs separated by a minimum of 12 weeks, thrombocytopenia, and continuous follow-up. Patients who developed thrombotic events were classified as the APS group, and a comparison was made between the clinical characteristics and prognosis of aPL carriers and patients with APS.

Study results revealed a higher proportion of smoking and hypertension in the APS group compared to aPLs carriers. Moreover, the platelet count of aPLs carriers at admission was lower than that of APS patients. The triple aPLs positivity was more prevalent in the primary APS cohort with thrombocytopenia.

“We compared the treatment response of the studied group and found that only the rate of CR was similar between aPLs carriers and patients with APS,” the authors highlighted.

The authors acknowledged several limitations in the study, including using a relatively small sample size that may cause the confidence interval to widen statistically and result in an underestimation of differences in clinical and biochemical findings. Further research is needed to investigate how the second hit can trigger thromboembolism.


Shi Y, Jiang H, Zhao Y. et al. Immune thrombocytopenia could be an independent clinical phenotype of antiphospholipid syndrome: a prospective cohort study. Rheumatol Ther. Published online February 20, 2023. doi: 10.1007/s40744-023-00538-0