Clinical and laboratory characteristics of children positive for antiphospholipid antibodies.

BACKGROUND: It is difficult to estimate the actual prevalence of antiphospholipid syndrome (APS) in the paediatric population since there are no standardised criteria. We aimed to assess clinical and laboratory characteristics of a cohort of children positive for antiphospholipid antibodies (aPL) to contribute to the understanding of the heterogeneous aPL-related features in childhood.
MATERIALS AND METHODS: Forty-four patients with prolonged activated partial thromboplastin time were enrolled and assigned to group I ("transiently positive") or group II ("persistently positive"), based on the detection of elevated aPL plasma levels [lupus anticoagulant (LA), anticardiolipin (aCL), and anti-β2-glycoprotein I (anti-β2GPI) antibodies] on, respectively, one or more occasions, at least 12 weeks apart, by standard procedures. The clinical history and symptoms of all patients were recorded.
RESULTS: Thirty-three (75%) patients were assigned to group I, while the other 11 (25%) formed group II. Major associated diseases in group I were urticarial vasculitis (21%), acute infections (18%) and thalassaemia (12%). Five subjects (15%) were asymptomatic. Four out of the 11 subjects (36%) in group II had thrombotic events; they were all persistently aPL-positive and two of them had concomitant systemic lupus erythematosus. The rate of detection of LA-positivity was not significantly different between the two groups (76% vs 91%, p>0.05), whereas the percentage of patients positive for overall aCL was higher in group II than in group I (54% vs 42%, respectively; p<0.05). Specifically, aCL IgG and anti-β2GPI IgM subtypes were significantly more represented in group II than in group I (100% vs 62% and 75% vs 33%, respectively; p<0.05). DISCUSSION: Our study shows that aPL-positive children have different features that should be taken into account in the classification of criteria for paediatric APS.