Immune thrombocytopenia (also called idiopathic thrombocytopenic purpura, immune thrombocytopenic purpura, ITP) is an acquired disorder. There are only two criteria required in order to make this diagnosis [1-6]:
- Isolated thrombocytopenia is present. The rest of the complete blood count, including an examination of the peripheral blood smear, is entirely normal, unless other coincidental abnormalities are present, such as iron deficiency.
- Clinically apparent associated conditions (eg, systemic lupus erythematosus, antiphospholipid syndrome, chronic lymphocytic leukemia) are not present. Patients with these associated conditions are described as having "secondary immune thrombocytopenia" . Also, drugs, including herbal remedies and quinine-containing beverages that may cause thrombocytopenia are NOT apparent etiologies.
The clinical manifestations, diagnosis, and differential diagnosis of ITP will be reviewed here. The treatment and prognosis of this disorder and the clinical manifestations, diagnosis, treatment, and prognosis of childhood ITP are discussed separately. (See "Treatment and prognosis of immune thrombocytopenia (ITP) in adults" and "Immune thrombocytopenia (ITP) in children: Clinical manifestations and diagnosis".)
The pathogenesis of ITP is related to a combination of increased platelet destruction along with inhibition of megakaryocyte platelet production via the production of specific IgG autoantibodies by the patient's B cells, most often directed against platelet membrane glycoproteins such as GPIIb/IIIa [2,8-11].
Inciting events — The etiology of ITP is unclear, but is thought to include genetic as well as acquired factors [7,12,13].