Idiopathic thrombocytopenic purpura (ITP): a historical odyssey.

Purpura has been recognized since ancient times and its clinical syndromes were refined by important observations in the sixteenth, seventeenth and eighteenth centuries. It required the development of adequate microscopes in the nineteenth century, however, to recognize the platelet, leading to the recognition of the thrombocytopenic component of ITP. The twentieth century brought recognition of the pathophysiology of the disorder and further defined the clinical states and treatments for ITP. The latter half of the twentieth century has focussed on the autoimmune components of ITP, initially on the humoral immune aspects and more recently on dysregulation of cellular immunity.