Normally the platelets are formed from megakaryocytes (stem cells) in the. bone marrow. These cells mature, fragment and are released in the blood stream. In idiopathic thrombocytopenic purpura there is rapid platelet destruction beacuse of presence of platelet antibodies which results in bleeding. There is no failure to produce platelets as there are abundant platelet precursors (megakaryocytes) in the bone marrow.
The child may present with petechiae ecchymosis, bleeding of the gums and epistaxis. Bleeding in the skin may be seen prominently over the legs. There may be hematemesis, malena, haematuria and haemarthrosis which indicate internal haemorrhage. There may also be occasional low grade fever. Anaemia may be present if there is significant blood loss. Diagnostic evaluation includes laboratory examination of blood which reveals platelet count below (40,000) 20,000/mm3 other platelet function tests such as tourniquet test, bleeding time and clot retraction is abnormal. The white blood cell count and cloting time is normal.