Epidemiology of incident immune thrombocytopenia: a nationwide population-based study in France.

The epidemiology of immune thrombocytopenia (ITP) is not well known. The purpose of this study was to assess ITP incidence at a nationwide level (France) with recent data (mid-2009 to mid-2011; 129 248 543 person-years). The data source is the French health insurance database. We selected cases with diagnosis codes for in-hospital stays and long-term disease attributions, thus restricting our search to ITPs necessitating health care. We studied incidence by age, gender, calendar month, regions, and proportion of secondary ITPs, of ITPs becoming persistent or chronic, and of severe bleeding at disease onset. We identified 3771 incident ITP patients. Incidence was 2.9/100,000 person-years, with peaks among children and in those >60 years of age. ITP was more frequent among males in these subgroups. The incidence was lower in overseas Caribbean French departments, suggesting a lower incidence among Afro-American people. There was a north-south gradient in mainland France and seasonal variations (peak in winter and nadir in summer). Persistence or chronicity occurred in 36% of children compared with 67% of adults. Among adults, 18% of ITPs were secondary. Malignancy was the main cause (10.9%). Myelodysplastic syndromes were not rare (2.3%). Severe gastrointestinal or central nervous system bleeding at ITP onset was rare (<1%).