Thrombocytopenia associated with pregnancy in a patient with type IIB von
Willebrand's disease
ME Rick, SB Williams, RA Sacher and LP McKeown
Thrombocytopenia may accompany variant (type IIB) von Willebrand's disease
(vWD) and is thought to result from binding of the abnormal von Willebrand
factor (vWF) to the patient's platelets with subsequent platelet aggregate
formation and clearance. We have studied a patient with type IIB vWD who
became thrombocytopenic during two pregnancies. During the third trimester
of pregnancy, her platelet counts dropped to 20,000 to 30,000/microL, and
an increase in the intermediate-sized vWF multimers was seen on agarose gel
electrophoresis. During this time her platelet-rich plasma showed
spontaneous platelet aggregation, and her plasma caused spontaneous
aggregation of normal washed platelets. Antibody to platelet glycoprotein
Ib completely blocked the spontaneous platelet aggregation, while antibody
to platelet glycoprotein IIb/IIIa did not block the response at the
concentrations used. Inhibitors of platelet function that elevate platelet
cyclic AMP also blocked the response, but aspirin had no effect on the
spontaneous platelet aggregation. The patient illustrates that the platelet
counts in one individual can vary greatly in type IIB vWD and that the
thrombocytopenia that occurs can appear under physiologic conditions that
stimulate the endogenous production of the patient's abnormal vWF. The
mechanisms leading to spontaneous platelet aggregation and thrombocytopenia
appear to be similar to those described for other patients with type IIB
vWD.
Volume 69,
Issue 3,
pp. 786-789,
03/01/1987
Copyright © 1987 by The American Society of Hematology
