Refractory Crohn-associated acute immune thrombocytopenic purpura treated with infliximab A proposed pathogenetic mechanism.

Immune thrombocytopenic purpura (ITP), either primary or secondary, is an autoimmune blood disorder characterized by platelet destruction due to the presence of antiplatelet antibodies. ITP, with fewer than 15 cases reported in the literature, is a particularly rare extra-intestinal manifestation of Crohn's disease. In both diseases, a state of activation of tissue macrophages and TH1 CD4 cells, either in the lamina propria of the gastrointestinal tract or systematically, is the dominant immunological feature. We describe for the first time a 69-year-old patient with ileocolonic Crohn's disease and the subsequent development of secondary acute ITP, refractory to steroids and immunoglobulins, that regressed under anti-TNFa (infliximab) infusion treatment. The common pathogenetic mechanism for both diseases and the mechanism of action of infliximab are discussed.