Introduction: New Directions in Hemostasis and Coagulation

Extract

The coagulation laboratory, like other departments in the clinical laboratory, is undergoing major shifts in both the understanding of the pathologic etiology of various diseases and the diagnostic procedures used in the definitive or differential diagnosis of these diseases. Much of this new information comes from advances in the identification of causative genes for the disorders, as well as from implementation of new diagnostic genetic and molecular procedures.

The term “thrombotic microangiopathies” (TMA) refers to clinical disorders characterized by the shared features of microangiopathic hemolytic anemia, thrombocytopenia, and microvascular thrombotic lesions. The period since 2002 has witnessed significant advances in the understanding of the entities included under TMA, particularly their genetics and pathophysiologic etiologies. Historically, hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) were the major clinical conditions included in a discussion of TMA. The two share certain clinical and pathologic features, and for a number of years it was recommended that the two be included within the combined clinical classification of “TTP-HUS”. However, the disorders appear to be different entities, with TTP associated with a severe deficiency of the von Willebrand factor cleaving protease ADAMTS-13, and familial and some sporadic cases of HUS associated with a deficiency of complement regulatory proteins. The current understanding of these two disorders is summarized in the following article by Margaret Schneider.

Medical textbooks have historically considered arterial and venous thromboembolic disease as distinct entities, with different pathophysiologic bases, unique risk factors, and distinct therapeutic approaches. However, a number of recent studies suggest…