Abstract
Immune thrombocytopenia (ITP) is an autoimmune disease characterized by a significant
reduction in the number of circulating platelets which is frequently associated with
bleeding. The total count of platelets in the body is finely regulated by the balance
between platelet production and destruction. Although the pathogenesis of ITP is still
not completely elucidated, it is largely recognized that the low platelet count observed
in ITP patients is due to alterations of both mechanisms. An abnormal proliferation
of autoreactive T cells leading to the breakdown of immune tolerance to platelet antigens
is suggested to be responsible for the up-regulated proliferation of autoantibody
producing B cells. Consequently, the immune response induces enhanced T cell-mediated
cytotoxicity and antibody-mediated platelet destruction through phagocytosis, complement
activation and apoptosis. An additional contribution to the pathophysiology of ITP
is given by alterations of thrombopoiesis caused by platelet-reactive autoantibodies
or cytotoxic T cells leading to impaired megakaryocyte differentiation and platelet
production. All these processes involved in ITP pathophysiology account for the complexity
and heterogeneity in the clinical manifestation and therapy responsiveness of this
disorder. For this reason, a better understanding of the different underlying mechanisms
in ITP is necessary to develop more efficient therapeutic treatments in the future.
In this review, we will provide an update on the pathophysiology of ITP with a particular
focus on the impact of impaired thrombopoiesis.
Keywords
autoantibodies - platelet - megakaryocytes - autoimmune disorders - acquired thrombocytopenia
