Background: Antiphospholipid syndrome (APS) is a systemic disease characterized by thrombotic manifestations and/or pregnancy morbidity in patients with persistent antiphospholipid antibodies (aPL). Besides macrovascular venous and/or arterial thrombosis, small vessel (SV) involvement may also be present due to the formation of clots in capillaries, arterioles and venules, potentially affecting any organ or system. Globally, SV can be targeted in up to 12% of APS patients [1].

Objectives: We aim to describe the manifestations related to SV involvement in a cohort of patients with APS followed at a Rheumatology tertiary center.

Methods: We included all patients with APS followed at a Rheumatology tertiary center from January 1996 until March 2024. Only patients meeting the Sydney classification criteria were included. Descriptive statistic was used to characterize the population, and the appropriate statistical tests to compare groups. Significance was set as an alpha<0.05.

Results: We included 85 patients with APS, 12 (14.1%) of whom with manifestations related to SV involvement (Table 1). Retinal involvement was found in 5 patients (5.9%): 2 retinal artery thrombosis, 1 retinal vein thrombosis and 2 cases of nongranulomatous ischemic optic neuropathy (ION). Central nervous system (CNS) microvascular lesions, aPL-valvular thrombus and livedoid vasculopathy were found in 5 (5.9%), 3 (3.5%) and 1 (1.2%) patients, respectively. No APS nephropathy or pulmonary microhemorrhages were reported in this cohort. SV involvement represented the presenting (and, to date, only) manifestation of APS in 1 patient - incidental findings of microvascular lesions on brain magnetic resonance imaging (MRI) performed due to suspicion of prolactinoma. One patient with SV disease died from non-APS related causes at 66 years old. Patients with SV involvement were older at disease onset (44.0±12.9 vs 33.8±13.5 years, p=0.018) and had more often a history of arterial thrombosis as the presenting manifestation (83.3% vs 26.4%, p<0.001). Patients with SV involvement used statins more frequently than the group without this involvement (66.7% vs 33.8%, p=0.031). No other differences were noted, including in what concerns sex, cardiovascular comorbidity, aPL profile or obstetric morbidity. Most patients with SV involvement (10/12, 83%) were treated with vitamin K antagonists (VKA). The remaining 2 were on low-dose aspirin (LDA): one due to asymptomatic microvascular CNS disease; the other one had ION but was non-compliant to anticoagulation due to a psychiatric disorder.

Conclusion: Around one in seven patients in our APS cohort had SV occlusions, which warrant prompt diagnosis and treatment. Our data suggest that particular attention should be given to these manifestations in older patients and those experiencing arterial thrombosis as the presenting manifestation. Larger and prospective studies are needed to confirm these findings.

REFERENCES: [1] Gaspar P, Sciascia S, Tektonidou MG. Epidemiology of antiphospholipid syndrome: macro- and microvascular manifestations. Rheumatology (Oxford). 2024 Feb 6;63(SI):SI24-SI36. doi: 10.1093/rheumatology/kead571. PMID: 38320589; PMCID: PMC10846913.

Acknowledgements: NIL.

Disclosure of Interests: None declared.

© The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.