PB0288 - Antiphospholipid syndrome in children: 30 years single-center prospective pediatric cohort from Argentina.

Background: Antiphospholipid syndrome (APS) is a rare condition in children characterized by thrombosis in the setting of persistently positive antiphospholipid antibodies (aPL). The classification criteria are extrapolated from adults and few studies have been reported in children.

Aims: To describe a pediatric cohort with APS at a single tertiary care pediatric center and to estimate thrombotic recurrence rate and its relative risk(RR) according to aPL profile.

Methods: From 1992 to 2022, consecutive < 18 year-old children with vascular thrombosis and the presence of aPL on ≥2 occasions ≥12 weeks apart were prospectively registered. Neonates and catastrophic APS were excluded.
Clinical data, laboratory results, treatment and outcomes were collected in a standardized data form.
aPL were tested according to the ISTH guidelines. Local cut-off values were used for each aPL.
Non-parametric statistics and a significance-level of p< 0.05 were used. Stata 15.0 was employed for statistical analysis.

Results: 39patients, 21(53.8%) females, median age 11.1years (0.1-17.4) were included. Patients´characteristics, laboratory results, treatment and outcomes are depicted in Table 1 and 2.
Inherited prothrombotic disorders were found in 2/28 patients studied. Two patients received no antithrombotic treatment due to thrombocytopenia. During a follow-up of 62.8months(6.3-228.7), recurrence rate was 25.6% (95%CI:11.9-39.3). Recurrent thrombosis was observed in 7/8patients (87.5%) with secondary APS and 6/8patients (75%) with double or triple aPL positivity.
The recurrence RR associated with double/triple vs simple positivity was 4.9 (95%CI: 0.70-35.8).
A statistically significant difference was found regarding age(p-value=0.004) and aPL persistence over time(p-value=0.0056) between infection-associated primary APS and secondary APS.

Conclusion(s): In this cohort with pediatric APS, most patients had deep vein thrombosis and lupus anticoagulant positivity. Patients with infection-associated primary APS were younger and had shorter persistence of aPL positivity. Thrombotic recurrence and death attributable to thrombosis were observed mostly in patients with secondary APS and mainly with a double or triple aPL positivity profile.