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Chapter 109. Disorders of Platelets and Vessel Wall (Part 10)

Patients with type 2 vWD have functional defects; thus, the vWF antigen measurement is significantly higher than the test of function. For types 2A, 2B, and 2M, vWF activity is decreased, measured as ristocetin cofactor or collagen binding activity. In type 2A vWD, the impaired function is due either to increased susceptibility to cleavage by ADAMTS13, resulting in loss of intermediate- and high-molecular weight (M.W.) multimers, or to decreased secretion of these multimers by the cell. Type 2B vWD results from gain of function mutations that result in increased spontaneous binding of vWF to platelets in circulation, with subsequent. | Chapter 109. Disorders of Platelets and Vessel Wall Part 10 Patients with type 2 vWD have functional defects thus the vWF antigen measurement is significantly higher than the test of function. For types 2A 2B and 2M vWF activity is decreased measured as ristocetin cofactor or collagen binding activity. In type 2A vWD the impaired function is due either to increased susceptibility to cleavage by ADAMTS13 resulting in loss of intermediate- and high-molecular weight M.W. multimers or to decreased secretion of these multimers by the cell. Type 2B vWD results from gain of function mutations that result in increased spontaneous binding of vWF to platelets in circulation with subsequent clearance of this complex by the reticuloendothelial system. The resulting vWF in the patients plasma lacks the highest M.W. multimers and the platelet count is usually modestly reduced. Type 2M results from a group of mutations that cause dysfunction of the molecule but do not affect multimer structure. Type 2N vWD reflects mutations in vWF that preclude binding of FVIII. As FVIII is stabilized by binding to vWF the FVIII in patients with type 2N vWD has a very short half-life and the FVIII level is markedly decreased. This is sometimes termed autosomal hemophilia. Type 3 vWD or severe vWD describes patients with virtually no vWF antigen usually 10 . Patients experience mucosal and joint postoperative symptoms as well as other bleeding symptoms. Some patients with type 3 vWD particularly those with large vWF gene deletions are at risk of developing antibodies to infused vWF. Acquired vWD is a rare disorder most commonly seen in patients with underlying lymphoproliferative disorders including monoclonal gammopathies of undetermined significance MGUS multiple myeloma and Waldenstrom s macroglobulinemia. It is seen most commonly in the setting of MGUS and should be suspected in patients particularly elderly patients with a new onset of severe mucosal bleeding symptoms. Heyde s syndrome .