Estimated fraction of the various forms of secondary ITP based on clinical experience of the authors. The incidence of Helicobacter pylori (HP) ranges from approximately 1 percent in the United States to 60 percent in Italy and Japan. The incidence of the HIV and hepatitis C virus approximates 20 percent in some populations. Miscellaneous causes of immune thrombocytopenia, for example, posttransfusion purpura, myelodysplasia, drugs that lead to the production of autoantibodies, and other conditions, are not discussed further in this chapter. Post marrow or solid-organ transplantation autoimmune lymphoproliferative syndrome (ALPS) occurred in approximately 1 percent of the authors’ patients. In the absence of a systematic analysis of the incidence of secondary ITP, the data shown represent the authors’ assessment based on our experience and the findings reported in the literature. APS, antiphospholipid syndrome; CLL, chronic lymphocytic leukemia, CVID, common variable immune deficiency; SLE, systemic lupus erythematosus. (Reproduced with permission from Cines DB, Bussel JB, Liebman HA, Luning Prak ET. The ITP syndrome: Pathogenic and clinical diversity. Blood 113(26):6511–6521, 2009.) Source: Thrombocytopenia, Williams Hematology, 9e Citation: Kaushansky K, Lichtman MA, Prchal JT, Levi MM, Press OW, Burns LJ, Caligiuri M. Williams Hematology, 9e; 2015 Available at: http://hemonc.mhmedical.com/DownloadImage.aspx?image=/data/books/1581/kau_ch117_f004.png&sec=142120518&BookID=1581&ChapterSecID=108081041&imagename= Accessed: October 22, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved