[Idiopathic thrombocytopenic purpura in children]

Idiopathic (immune) thrombocytopenic purpura (ITP) is the most frequent hemorrhagic disease in children. It represents the acquired megakaryocytic thrombocytopenia with the shortened life of platelets because of immunologic damage (antibodies absorbed by platelets). In the case of this acquired hemorrhagic disorder, in spite of compensatory increased function of the bone marrow, there is a reduced number of platelets because of their increased destruction by the reticuloendothelial system (destructive thrombocytopenia). There are three forms of ITP: acute, chronic and intermittent. The acute form occurs in 80-90% of cases with bleeding episodes lasting a few days or weeks, but no longer than 6 months. The chronic form occurs in 10-15% of children, while the rarest-intermittent form is characterized by periods of normalization in regard to the number of platelets but also with relapse in intervals of 1-3 months. The disease is caused by an immunological disorder in the sense of an imbalanced immune response. Immunologic damages of platelets cause shortening of the opsonized platelets life span. The most frequent platelet opsonins are the immumoglobulin G (IgG) antibodies directed at the platelet membrane in the form of autoantibodies, alloantibodies or possibly absorbed antigen caused by microorganism infection or drug intake.

It is typical for the phenomenon of bleeding that it starts suddenly and without any other sign of illness. The most frequent acute form appears between the second and fourth year, and is characterized by seasonal occurrence usually after acute viral infections. Children older than 10 years of age, like adults, often have the chronic form associated with other immunologic disorders. The disease affects girls more often than boys (about three times more often) with moderate and constant increase of antiplatelet antibodies. Hemorrhagic manifestations include: petechiae, purpura, epistaxis, gastrointestinal and genitourinary bleeding. They depend on the grade of thrombocytopenia, although there is no strict correlation between the number of platelets and volume of bleeding. Low mortality of the acute ITP is almost exclusively due to intracranial hemorrhage. LABORATORY STUDIES: Thrombocytopenia represents a decrease in the number of blood platelets being a basic abnormality of the blood count. The half-life of platelets in ITP is shortened. Detection of antiplatelet antibodies is connected with technical difficulties, so they are established in about 30% of cases. Bleeding time is prolonged and so is the coagulum retraction which may be completely missed. The Rumpel-Leede test is positive. Clinical differentiation of drug-induced thrombocytopenia is not possible. However, other differential diagnostic possibilities are thrombotic-thrombocytopenic purpura and hemolytic-uremic syndrome. A child with aplastic anemia or acute leukemia, beside thrombocytopenia, has a characteristic finding of white and red blood cell count. Thrombocytopenia with absent radii syndrome is associated with skeletal system abnormalities.

New knowledge about the role of the immune system in ITP determines the modern therapeutic modalities. In cases of acute ITP in children, there are two therapeutic options or therapies of choice: corticosteroids and high doses of intravenous immunoglobulin. Immunosupressive therapy means anti Rh(D) immunoglobulin, cyclosporine, cytostatics, danazol, loaded platelets. In cases of distinctive hemorrhagic syndrome there are also indications for platelet transfusion. Nowadays splenectomy is more restricted, because one third of cases is unsuccessful, whereas plasmapheresis is rarely used in children because of possible complications.

ITP is the most frequent hemorrhagic disease in children. The disease is basically caused by an immunologic disorder with platelet destruction due to increased immunoglobulin on their membrane. (ABSTRACT TRUNCATED)