The clinical relevance of different antiphospholipid antibody profiles in pediatric rheumatology patients

The clinical relevance of different antiphospholipid antibody (aPL) profiles, including low level anticardiolipin (aCL) and anti-β₂-glycoprotein-I (aβ₂GPI) antibodies, is ill-defined in the pediatric population. Our purpose is to describe the demographic, clinical, and laboratory characteristics of aPL positive pediatric patients based on different aPL profiles.

In this single center retrospective cohort study, based on the screening of our pediatric (age ≤ 18) rheumatology electronic medical records (2016–2022), we identified patients who had at least one “positive” aPL (lupus anticoagulant [LA], aCL IgG/M, or aβ₂GPI IgG/M) result. Patients were grouped into high- (LA positive and/or aCL/aβ₂GPI IgG/M > 40U [ELISA]) and low-risk (LA negative and aCL/aβ₂GPI IgG/M 20-39U) aPL profiles; those with persistently positive aPL were descriptively analyzed for demographic and clinical characteristics. Of 57 included patients, 34 (59%) had initial high- and 23 (40%) had initial low-risk profiles. Based on subsequent aPL results available in 42/57 (74%) patients, 25/27 (93%) in the high-, and 7/15 (47%) in the low-risk groups remained still positive. Of these 32 patients with persistently positive aPL, moderate-to-large vessel or microvascular thrombosis occurred in nine (28%) patients with high-risk and in none with low-risk aPL profiles; non-thrombotic aPL-related manifestations were reported in 15 (47%) patients with persistent aPL positivity.

An initial high-risk aPL profile was persistent in approximately 90% of our cohort, a third of whom had thrombosis, and half had non-thrombotic aPL manifestations. Our results underscore the need for a large-scale effort to better characterize aPL-related manifestations in pediatric patients with persistent high-risk aPL-profiles.