The objective of the study is to produce a dynamic picture of the adult ITP natural history and management in Italy by collecting standardized information retrospective and prospective data of patients in active management through a nation-wide registry.

Primary immune thrombocytopenia (ITP) is an acquired autoimmune disorder affecting both children and adults, characterized by a platelet count below 100 x 109/L in the absence of any underlying disease explaining the thrombocytopenia. Clinical manifestations may be absent or include cutaneous mucosal or organ bleeding, resulting in an overall mortality rate of less than 1-2%.

Previously, 'acute ITP' was used to describe a self-limited form of the disease and 'chronic ITP' to describe the disease if it lasted for more than 6 months. In 2009, a new terminology for ITP was agreed upon based on the duration of the disease. The new terms for ITP are: 'newly diagnosed ITP (from diagnosis to 3 months), 'persistent ITP' (3-12 months) and 'chronic ITP' (lasting for more than 12 months) [2].

Chronic primary ITP in adults is slightly more common in women of childbearing age but the sex incidence is similar in patients over 60. The incidence of ITP in adults is around 4 per 100.000 people per year, with a UK prevalence of up to 24 per 100.000 people [4-6]. No more than 2 per 100.000 will require ITP treatment.

Bleeding is highly variable and there is great heterogeneity. Bleeding is most commonly mucocutaneous, involving the skin and subcutaneous tissue (petechiae, ecchymoses, subcutaneous hematomas), the external mucosae (epistaxis, gum bleeding, blood blisters in the mouth), muscles (muscle hematomata) or the various organs and internal mucosae (hematuria, gastrointestinal bleeding, menorrhagia, intracerebral bleeding). Major bleeding is not common if the platelet count is above 30x109/L. Intracranial hemorrhage is rare and is most often seen in older patients who have additional comorbidities and in patients who fail to respond to therapy. The yearly risk of fatal hemorrhage is around 1.6-3.9% in unresponsive patients. This risk varies with age, from 0.4% per year in patients below 40 years old to 13% per year in those over 60. The natural history of ITP with currently available treatments is not well known. Available data are mostly based on the era when rituximab and thrombopoietin-receptor agonists (TPO-RA) were not in use.

There is a lack reliable data on how recent treatments have modified the course of the disease. Bleeding frequency and severity, complications like infections, thrombosis, ITP-related symptoms like fatigue, etc. are also largely unknown as are women's related issues. Similarly, the cost of treatment for a patient with ITP is not available. Safety and efficacy of specific recent treatments have been measured mostly in industry-sponsored studies. Furthermore, most studies did not conform to the International Working Group (IWG) on ITP recommendations concerning terminology, definitions, outcome criteria and assessment of bleeding.

To the investigator's knowledge, an ITP Registry is ongoing in UK and in Australia and registries are being planned in other European countries with a prospective of creating an international network. The only established international registry, the ITP PARC study, is operative since 2004 but covers different aspects of the disease. The few Italian registries are of regional dimension and are not aligned to collect standardized information in a uniform way.

Inclusion Criteria:

• Patients never treated before for whom an ITP treatment is initiated for the first time by the recruiting center
• Patients already treated for whom a new line of ITP treatment is initiated by the recruiting center (the patients could have been treated elsewhere before)
• Patients who, under any ITP treatment at the recruiting center.

Exclusion Criteria:

-Undefined

All consecutive adult patients (18 years or older) in active treatment for ITP meeting one of the three conditions at their first visit after the enrolment has been opened.

In all cases, patients should be enrolled at the first visit during the enrolment period (or at latest within 1 month with data referred back to the first visit).