American journal of clinical pathology
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Am. J. Clin. Pathol. · Oct 1989
Case ReportsAbsence of a bleeding tendency in severe acquired von Willebrand's disease. The role of platelet von Willebrand factor in maintaining normal hemostasis.
A 67-year-old male with a prolonged activated partial thromboplastin time (APTT) of 43 seconds (normal, 25-40 seconds) was found to have laboratory features of von Willebrand's disease and IgA myeloma but had a normal bleeding time and no bleeding tendency. Plasma Factor VIII coagulant activity (F. VIII:C) was 80 U/L (0.08 U/mL), Factor VIII antigen (F. ⋯ VIII deficiency results from complexing of the IgA myeloma protein with vWF, resulting in premature clearance of the vWF/F. VIII complex. The absence of clinical bleeding likely results from the combination of a normal platelet vWF:Ag level and persistence of intermediate molecular weight vWF multimers.