The incidence of ITP is estimated at 50–100 new cases per million per year, with children accounting for half of that number.  At least 70 percent of childhood cases will end up in remission within six months, even without treatment.  Moreover, a third of the remaining chronic cases will usually remit during follow-up observation, and another third will end up with only mild thrombocytopenia (defined as a platelet count above 50,000). A number of immune related genes and polymorphisms have been identified as influencing predisposition to ITP, with FCGR3a-V158 allele and KIRDS2/DL2 increasing susceptibility and KIR2DS5 shown to be protective.