INTRODUCTION

This chapter focuses on the immune, nonimmune, acquired, and hereditary thrombocytopenias. In particular, it covers immune thrombocytopenic purpura (ITP) and alloimmune thrombocytopenia (AIT) in the fetus and newborn. However, an attempt is made to discuss all of the clinically significant thrombocytopenias. References to more detailed reviews and to specific articles in certain areas are provided. Areas that would benefit from additional research are highlighted as well.

IMMUNE THROMBOCYTOPENIC PURPURA

After chemotherapy-induced thrombocytopenia, ITP is among the most common causes of acquired thrombocytopenia. It has been estimated to affect approximately 1 in 10 000 in the general population, about half of whom are children, and to account for 0.18% of hospital admissions. ITP is caused by autoreactive antibodies that bind to platelets, shorten their life span, and, in an unknown percentage of cases, impair platelet production.

The clinical presentation of ITP varies from the acute onset of severe thrombocytopenia and important mucosal bleeding to the discovery of mild asymptomatic thrombocytopenia during evaluation of another illness or on a routine checkup. ITP can occur as an isolated, “idiopathic” condition or it may accompany other systemic disorders, such as systemic lupus erythematosus (SLE) or chronic lymphocytic leukemia. Considerable progress has been made in understanding the pathophysiology of ITP. Several new treatment modalities have been introduced during the past 5 to 10 years.