Anti-beta2-glycoprotein I in childhood immune thrombocytopenic purpura.

Immune thrombocytopenic purpura (ITP) etiology is not clarified. Phospholipid antigen antibodies (aPls) occur in ITP patient sera. We studied predictive values of elevated anti-beta2-glycoprotein I (anti-beta2-GP1) or anticardiolipin antibody (aCl) concentrations for secondary ITP detection, comparing levels with steroid therapy responsiveness in three groups of children and adolescents. Participants' antinuclear antibodies, aCls (IgM, IgG) and anti-beta2-GPI (IgG) were assessed. Significantly higher aCl (IgM), aCl (IgG) and anti-beta2-GPI (IgG) mean concentrations occurred in chronic ITP cases compared with acute or control cases. Of chronic ITP cases, 77.8% showed elevated IgG aCl serum concentrations, and all presented increased IgG anti-beta2-GPI serum levels. Significant positive correlation between increased levels of IgG anti-beta2-GPI and increased IgG aCl serum concentrations was determined; these increased IgG concentrations significantly correlated with steroid therapy resistance. A total of 76.1% of ITP cases had positive aPls (all chronic ITP cases, five acute ITP cases). Elevated aCl or anti-beta2-GPI serum IgG isotype concentrations occurred in all nine splenectomized ITP children with positive aPls (three showed increased IgM aCl levels). Follow-up of the initially studied ITP children (2000-2004) revealed 16.7% developed clinical and laboratory criteria of systemic lupus erythrematosus (one acute ITP in remission, six chronic ITP); elevated IgG aCl serum concentrations were found at study start in these seven cases, and six had increased anti-beta2-GPI. IgG classes of both aCls and anti-beta2-GPI may be determinant cofactors for the developing risk of antiphospholipid syndrome or autoimmune diseases in ITP. Great attention should be paid to both assays as predictors for steroid therapy response.