Von Willebrand factor (VWF) is an adhesive multimeric plasma glycoprotein (GP) that mediates platelet adhesion to injured subendothelium via GPIbα, and binds and stabilizes factor VIII (FVIII) in the circulation, protecting it from proteolytic degradation. This important multifunctional protein was…
In 1924, Moschowitz reported a case of a 16-year-old girl who died of a previously undescribed illness characterized by microangiopathic hemolytic anemia (MAHA), petechiae, hemiparesis, and fever. Postmortem examination revealed numerous hyaline thrombi, most prevalent in the terminal arterioles and…
Heparin-induced thrombocytopenia (HIT) is the most important drug-induced immune-mediated cytopenia for several reasons. First, heparin is a widely used anticoagulant (see Chapter 143 ). Second, HIT is relatively common, occurring in approximately 1% to 3% of postoperative patients, and 0.2%…
Thrombocytopenia is defined as a platelet count below the lower limit of the normal range (≈150 × 10 9 /L). Sometimes, an expanded definition of thrombocytopenia is appropriate. For example, an abrupt drop in the platelet count can signify the…
Platelets are anucleate cells that are required for primary hemostasis. A normal platelet count is 150,000 to 400,000 platelets per microliter of blood, with a normal lifespan of 7 to 10 days for circulating platelets. The body clears 10 11…
Acquired disorders of platelet function are among the most common hematologic abnormalities, which reflects the sensitivity of platelets to external and internal perturbations. The clinical challenge in evaluating acquired disorders of platelet function is to determine whether observed derangements in…
This chapter provides a practical approach to the laboratory evaluation of hemostatic and thrombotic disorders. Any assessment of hemostatic or thrombotic disorders must start with a thorough history and physical examination. These can provide clues to guide subsequent laboratory testing,…
Bruising and bleeding are common reasons for a hematology referral. Some consults are for management of an acute bleed in someone who may have a hemorrhagic disorder. Such bleeds may be spontaneous or occur after surgery or trauma, and the…
Blood is the principal vehicle delivering oxygen and nutrients to the various tissues and organs of the body. Blood flow and the integrity of the vasculature are essential to life itself. The hemostatic process has evolved to provide damage recognition…
A primary physiological role of platelets is to support hemostasis at sites of vascular injury by forming a plug that arrests blood loss ( Fig. 124.1 ). Normally, disc-shaped platelets circulate in the bloodstream without adhering to the endothelium of…