[Epidemiology and pharmacoepidemiology of immune thrombocytopenia]

During the last decade, the development of large clinical and population-based cohorts led to new findings in the epidemiology and the pharmacoepidemiology of immune thrombocytopenia (ITP). The incidence is estimated to 3-4 for 10⁵ inhabitants/year, with a slight female predominance and peaks in children and patients after 60 years. The incidence rate is 9 for 10⁵ inhabitants/year in males after 75 years. Variations across ethnic groups are discussed. In France, there is a North-South gradient and a peak of incidence during winter suggesting the role of viruses in ITP pathophysiology. Myelodysplastic syndromes are an emergent cause of secondary ITP. The incidence of intracranial bleeding is about 1% by year and the risk increases with aging. Exposure to splenectomy decreases while rituximab and thrombopoietin receptor agonists (TPO-RA) are the most used second-line drugs for persistent ITP. Mortality is slightly increased in primary ITP as compared with the general population. ITP patients have an increased risk of infection, thrombosis and hemorrhage. Aging, lung diseases, splenectomy, corticosteroids and rituximab are risk factors for infection while influenza and pneumococcal vaccines are associated with a 50% decrease of infection risk. Aging, cardiovascular risk factors, lupus anticoagulant and splenectomy are risk factors for thrombosis. The risk of thrombosis associated with corticosteroids and TPO-RAs must be further investigated.