Acute immune thrombocytopenic purpura (ITP) induces thrombocytopenia by means of an autoimmune mechanism. Recent studies suggested that T helper immune response is responsible for the pathogenesis of chronic ITP. Despite several studies that were carried out, we do not have a clue as to what triggers the autoimmunity. Leptin is a 16-kd protein secreted from the adipose tissue. Leptin is structurally similar to interleukin (IL)-2, IL-6, and IL-15. The structural similarities between leptin receptor and hematopoietic cytokine receptors suggested that leptin could play a role in hematopoiesis and immune function. Recent studies suggested that leptin could play an important role in autoimmunity. We made a prospective analysis of a series of 39 newly diagnosed acute childhood ITP in a year period. Serum leptin levels were obtained after diagnosis and before treatment and all patients were followed up at least 6 months to designate acute or chronic event. We conclude that in childhood acute ITP, leptin did not play a role in the pathophysiology of the disease. Further investigations are needed to examine what triggers T cells and how the autoimmune disease became.