MCQ Hematology Answer 15

Answer: D

Although the history initially suggests ITP, further questioning indicates that the patient has a life-long bleeding history and that her father may have a bleeding disorder. Additionally, the patient did not respond to treatment with prednisone.

Although the results of the VWF activity and antigen were within the normal reference range, they should be increased above normal (approximately twice normal) at this point in the patient’s pregnancy.

Type 2B VWD can cause this clinical picture with worsening thrombocytopenia during pregnancy; this is due to the increased synthesis of VWF that normally occurs in later pregnancy, leading to a higher level of the abnormal VWF in the circulation that binds to platelets and causes small aggregate formation and clearance of the platelets.

A VWF multimer study will reveal a decrease in the highest molecular weight multimers of VWF. A ristocetin-induced platelet aggregation study can be attempted, but the low platelet numbers would likely make this test difficult to interpret (one would expect aggregation with low concentrations [<0.60>

Platelet aggregation studies would be difficult to carry out due to the low count, and the size distribution of platelets will not yield a specific diagnosis. The thromboelastogram test also will not indicate a specific diagnosis, and a bleeding time will be prolonged due to the low platelet count.

Reference:

1. Rick ME, Williams SB, Sacher RA, McKeown LP. Thrombocytopenia associated with pregnancy in a patient with type IIB von Willebrand’s disease. Blood 1987; 69:786-89.

Category: Hematology MCQs