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.

Inclusion Criteria:

• Children as young as 2 months of age and adults in follow-up since 2015 (irrespective of date of diagnosis) with the diagnostic presumption of PIT or other thrombocytopenia of probable immune origin defined as a platelet count < 100 x 109/L.
• Patients who have given written informed consent. In the case of deceased patients, the data will be included in the registry and the investigator will record the impossibility of collecting patient's informed consent form due to death. Only patients deceased after December 31 2015, will be included

Exclusion Criteria:

• Patients who, at the investigator's discretion, do not meet the conditions for inclusion in the study

People with the diagnostic presumption of PIT or other thrombocytopenia of probable immune origin defined as a platelet count < 100 x 109/L.