Transient and chronic childhood immune thrombocytopenia are distinctly affected by Fc-γ receptor polymorphisms.

In childhood immune thrombocytopenia (ITP), anti-platelet autoantibodies mediate platelet clearance through Fc-γ receptor (FcγR)-bearing phagocytes. In 75% to 90% of patients, the disease has a transient, self-limiting character. Here we characterized how polymorphisms of FcγR genes affect disease susceptibility, response to intravenous immunoglobulin (IVIg) treatment, and long-term recovery from childhood ITP. Genotyping of the locus was performed in 180 children with newly diagnosed ITP, 22 children with chronic ITP, and 180 healthy control children by multiplex ligation-dependent probe amplification. Children with newly diagnosed ITP were randomly assigned to a single administration of IVIg or observation, and followed for 1 year (Treatment With or Without IVIg for Kids With ITP [TIKI] trial). We defined transient ITP as a complete recovery (≥100 × 10/L) 3 months after diagnosis, including both self-limiting disease/IVIg responders and chronic ITP as absence of a complete recovery at 12 months. ITP susceptibility, as well as spontaneous recovery and response to IVIg, was associated with the genetic variants *ORF and *27W and the promoter variant 2B.4. These variants were overrepresented in patients with transient (N = 131), but not chronic (N = 43), disease. The presence of *ORF predisposed to transient ITP with an odds ratio of 4.7 (95% confidence interval, 1.9-14.3). Chronic ITP was associated with a deletion of (copy number region 1) with an odds ratio of 6.2 (95% confidence interval, 1.8-24.7). Taken together, susceptibility to transient and chronic ITP is distinctly affected by polymorphic variants of genes. Our data suggest that genotyping of the locus may be useful for prognosis and guidance of treatment decisions in newly diagnosed childhood ITP.