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In recent years, antiphospholipid antibodies (aPL) and their associated clinical features have been recognized increasingly in various pediatric autoimmune and non-autoimmunediseases. Pathogenic mechanisms involved in pediatric antiphospholipid syndrome (APS) appear to be the same as inadults. However, since pediatric patients do not have prothrombotic risk factors present in adults, there clearly are differences in the spectrum of clinical findings. The frequency of aPL-related thrombotic events is generally low in pediatric populations. On the other hand, various commonly acquired infections are likely to be responsible for higher percentage of non-pathogenic and transient aPL in childhood. Such points have to be considered in clinical judgment of elevated aPL in children. In this review we summarize the recent data on the prevalence and clinical significance of aPL in neonates, children and adolescents.

OBJECTIVES To determine anticardiolipin (aCL) and anti-beta(2) glycoprotein I antibodies (anti-beta(2)GPI) in apparently healthy children and express the cut-off levels in concentrations of monoclonal antibodies, and to compare the mean values and frequencies of aCL and anti-beta(2)GPI in children with those in blood donors. METHODS Blood samples were collected from 29 preschool children and 32 adolescents during their routine preventive follow-up visits. The control group consisted of 52 blood donors. aCL and anti-beta(2)GPI were assayed by an ELISA method. Two monoclonal beta(2)GPI-dependent aCL (HCAL and EY2C9) were used as calibrators. RESULTS The estimated cut-off values for immunoglobulin G (IgG) and immunoglobulin M (IgM) aCL, expressed in concentrations of monoclonal antibodies and standardized international units (GPL/MPL units), were 13.9 ng/ml (7.6 GPL) and 33.1 ng/ml (3.3 MPL) for preschool children, 13.5 ng/ml (7.2 GPL) and 36.9 ng/ml (4.0 MPL) for adolescents, and 14.4 ng/ml (8.0 GPL) and 42.6 ng/ml (5.1 MPL) for blood donors. No statistically significant differences in the mean values for IgG and IgM aCL were found between the age groups. The mean value of IgA aCL was significantly higher in blood donors than in preschool children and adolescents (P<0.037 and P<0.025 respectively). Seven (11.4%) of 61 apparently healthy children had low positive values for aCL (IgG for all seven). The estimated cut-off values for IgG and IgM anti-beta(2)GPI were 4.2 and 13.1 ng/ml respectively for preschool children, 3.2 and 13.1 ng/ml for adolescents, and 2.9 and 20.5 ng/ml for blood donors. The mean value for IgG anti-beta(2)GPI was found to be higher in preschool children than in adolescents and blood donors (P<0.0001 and P<0.0001). The mean values for IgM and IgA anti-beta(2)GPI were higher in blood donors than in preschool children (IgM, P<0.007; IgA, P<0.0001) and adolescents (IgM, P<0.01; IgA, P<0.0001). Four (6.6%) of 61 apparently healthy children had positive values for anti-beta(2)GPI (two for IgG and two for IgA). CONCLUSIONS This is the first report in which the cut-off values for aCL and anti-beta(2)GPI in children are expressed in concentrations of monoclonal antibodies. Low titres of aCL, which were identified frequently in apparently healthy children, were hypothesized to be the result of previous infections. The high mean value of IgG anti-beta(2)GPI observed in preschool children was an unexpected result of the study and might indicate a default response to nutritional exposure to beta(2)GPI in this age group.

An outbreak of acute hepatitis of unknown aetiology in children was reported in Scotland 1 in April 2022 and has now been identified in 35 countries 2 . Several recent studies have suggested an association with human adenovirus with this outbreak, a virus not commonly associated with hepatitis. Here we report a detailed case–control investigation and find an association between adeno-associated virus 2 (AAV2) infection and host genetics in disease susceptibility. Using next-generation