It has been suggested that, for purposes of etiologic investigation, thrombocytopenic purpura be separated into its two component parts, thrombocytopenia and purpura, and that they be regarded as two coexisting abnormalities rather than as a single disease. Historical review of the development of knowledge of the pathogenesis of purpura emphasizes the importance and soundness of this dual approach. Both thrombocytopenia and purpura have been shown to have a complex etiologic pattern with multiple potential etiologic factors. The curious similarity of these two groups of factors may at least partially explain the frequent coexistence of the two abnormalities in the clinical picture of thrombocytopenic purpura.
It has been shown that allergy has long been recognized as an etiologic factor of major importance in both purpura and thrombocytopenia. It is logical, therefore, that it should frequently be an important etiologic factor when the two conditions exist together, and it is suggested that when diagnostic methods are more adequate a considerable number of cases of "idiopathic" thrombocytopenic purpura will fall into that category and will yield therapeutically to a proper allergic approach.