[Diagnostic approach and treatment of immune thrombocytopenia in adults]

The aim of this review is to provide the Croatian medical public with novel insights into the definition, pathogenesis, diagnostic algorithms and treatment approaches to immune thrombocytopenia (ITP) in adults. Recently, primary ITP has been uniformly defined as an autoimmune disorder characterized by an isolated platelet count lower than 100 x 10(9)/L without preexisting disease or conditions, which could lead to thrombocytopenia. The recognition of primary and secondary ITP is important because they require different treatment strategies. In secondary ITP, therapeutic approach oriented towards the underlying disorder. Unlike childhood onset ITP, which is a self-limited condition with high rates of spontaneous remissions, adulthood onset ITP usually has chronic course. Previously, the pathogenesis of ITP was considered to be immune mediated destruction of platelets in liver and spleen, while recent findings have shown a novel pathophysiological pathway based on the inhibition of thrombopoiesis, leading to novel treatment approaches. The diagnosis of ITP is based on exclusion of the possible underlying causes of thrombocytopenia and consists of simple diagnostic procedures. The decision to treat ITP should be based individually: platelets count (lower than 30 x 10(9)/L), various bleeding risk factors and patient's preference. The use of corticosteroids is the mainstay of first line therapy. Two most commonly used corticosteroids are prednisone and dexamethasone. Prednisone is administered continuously, while dexamethasone is applied in cycles. Due to the lack of randomized clinical trials, it is not possible to recommend certain class of corticosteroid therapy. Another two agents used as first line therapy in case of corticosteroid refractoriness or the need of rapid platelet elevation, are intravenous immunoglobulins and anti-D immunoglobulin (anti-D is not approved in Europe). They are characterized by rapid onset of platelet recovery and low long-term remission rates. Until recently, splenectomy, with adequate infectious and thromboprophylaxis, was the therapy of choice in patients who did not respond to corticosteroids due to high long-term remission rates and low relapse rates. This procedure can be offered to a younger patient without significant comorbidities after the first year of ITP duration. With advances in the understanding of ITP pathogenesis, a new class of drug has been established: thrombopoietin agonists (TPO). Eltrombopag and romiplostim, the TPO agonists currently approved for the management of ITP in patients who failed the first line therapy and are not suitable for splenectomy, are only two agents that have shown benefits in large clinical randomized trials. They are characterized by a high response rate and appropriate safety profile, but the need for continuous use, a high relapse rate after therapy withdrawal, and price limit their use in everyday practice. TPO agonists represent an appropriate treatment choice in patients who have relapse after splenectomy. Another agent, often used in everyday clinical practice, is rituximab with high response and relapse rates. Its use is based on small studies, and due to the lack of clinical randomized controlled trials, rituximab is not approved by the leading medical agencies for this indication. As shown in this review article, our understanding and therapy for ITP has improved, but further research is needed to implement evidence-based therapy in clinical practice.