Primary immune thrombocytopenia (PIT), previously referred to as idiopathic thrombocytopenic purpura, is an acquired disease characterized by accelerated platelet destruction and deficient platelet production by megakaryocytes. Although the existence of PIT has been known for decades, there is no consensus on its triggering mechanisms. On the other hand, this disease presents a very heterogeneous patient profile, both in its characteristics and treatments. In this sense, the diagnosis is still made by excluding other causes of thrombocytopenia. There is insufficient epidemiological data on the disease, a fact that is especially evident in our country. We have no data on the incidence or prevalence of this pathology in Spain. For all these reasons, this epidemiological study has been designed to increase the available knowledge about this disease and the detailed characterization of the population of patients with ITP in Spain. The main objective of this study is to describe the clinical, analytical and treatment characteristics of primary immune thrombocytopenia and other immune thrombocytopenia. The study is an epidemiological, ambispective, multicenter study carried out in hospitals in Spain. Information will be collected on the disease under study, as well as on the treatments received, using the patient's clinical history as a source document.