Idiopathic thrombocytopenic purpura

Abstract

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder caused by platelet-reactive antibodies that lead to the development of thrombocytopenia and eventuate in mucosal bleeding (1). The exact incidence is uncertain. It is estimated that approximately 100 new cases are diagnosed per 1,000,000 persons each year (2-5), divided roughly equally between adults and children. Although adult-onset ITP and ITP manifesting in early childhood are both caused by platelet autoantibodies, their natural histories and possibly their etiologies differ. In adults, ITP occurs more commonly in females and the disorder tends to run a chronic course, whereas in children both sexes are equally affected and spontaneous remissions are common. There are also important differences in the differential diagnosis and management. Therefore, we will consider ITP diagnosed in these two age groups separately. Another important distinction is between ITP that occurs as an isolated condition (primary ITP) and ITP that occurs in the context of several well-described predisposing conditions (secondary ITP). This chapter will focus on primary ITP, but the salient features of common forms of secondary ITP will be noted where appropriate. Several recent reviews have appeared (5a,5b).