Immune thrombocytopenia (ITP) is an acquired autoimmune disorder
characterized by a platelet count of less than 100 x 109 platelets/L. ITP results from two
distinct processes: accelerated platelet destruction and reduced platelet production. A
distinction of the relative contribution of these pathologies should help guide more
targeted treatment decisions. Mechanistically, decreased platelet production is caused
by autoantibody-mediated damage to megakaryocytes, while increased clearance of
antibody opsonized platelets has traditionally been attributed to the activity of splenic
and hepatic macrophages. T cell mediated toxicity has also been described as a
contributor to ITP pathogenesis. Recent observations of increased platelet apoptosis
and glycoprotein desialylation associated with platelet clearance by hepatocytes
provide new avenues for therapeutic intervention. The aim of ITP therapy is to attain
sufficient platelet levels to achieve haemostasis. Significant improvements have been
obtained with first line therapies such as corticosteroids and intravenous
immunoglobulins. For unresponsive patients, second line therapies (splenectomy,
rituximab, TPO receptor agonists) have proved beneficial. Nevertheless, the
heterogeneous nature of ITP demands further understanding of the causal biological
processes to provide personalized and more effective therapies. This chapter presents
an account of the current understanding of the biology of ITP and discusses the existing
and potential new treatments.
Keywords: Apoptosis, Autoantibodies, Autoimmunity, Desialylation, Immune
thrombocytopenia, Immune thrombocytopenic purpura, ITP, IVIg,
Megakaryocyte, Platelets, Splenectomy, Thrombopoiesis, TPO receptor agonists.
