Extramedullary haematopoiesis in thrombotic thrombocytopenic purpura

Extramedullary hematopoiesis was detected in routine sections of spleen and liver from two patients with thrombotic thrombocytopenic purpura (TTP). In patients with other types of hemolytic anemia and in normal persons, extramedullary hematopoiesis was not found in spleen or liver. The results of this study raise the possibility that TTP may fit within the myeloproliferative category, perhaps representing an acute variant of Di-Guglielmo Syndrome.