Von Willebrand factor-cleaving protease activity and proteolysis of von Willebrand factor in bone marrow transplant-associated thrombotic microangiopathy.
BACKGROUND
Thrombotic microangiopathy (TM) of the fulminant type occurring in patients following bone marrow transplant (BMT) has clinical manifestations that are similar to thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome, but the outcome is generally fatal despite conventional therapy. Idiopathic acquired TTP has been associated with IgG inhibitors to the cleaving protease of von Willebrand factor (vWF) in plasma. In this study, we investigated the role of the vWF protease and vWF proteolysis in the pathogenesis of BMT-associated TM of the fulminant type.


METHODS
vWF antigen level, vWF multimeric pattern, and vWF metalloprotease activity were investigated in the plasma samples of six consecutive patients with acute BMT-associated TM. Histologic and immunohistochemical studies were also performed on autopsy kidney specimens from four of the patients. All six patients had the fulminant type of the disorder with a fatal outcome and none of the patients responded to plasma infusion.


RESULTS
The vWF-cleaving protease activity in plasma was normal in all patients. However, analysis of the vWF multimeric pattern showed a decrease of high molecular weight multimers. The decrease of large multimers may be caused by vWF-platelet binding as well as shear enhanced proteolysis of vWF. In the four patients who had an autopsy, a pattern of arteriolar thrombosis, distinct from that of TTP, was detected in the kidneys.


CONCLUSIONS
These findings suggest that BMT-associated TM of the fulminant type is a heterogeneous process and distinct from TTP in pathogenesis. Analysis of vWF protease and vWF multimeric distribution are valuable tools in making the distinction between BMT-associated TM and TTP.
Arai
S
S
Johns Hopkins Oncology Center, Johns Hopkins Hospital, Baltimore, Maryland 21231-1000, USA. araisa@jhmi.edu
Allan
C
C
Streiff
M
M
Hutchins
G M
GM
Vogelsang
G B
GB
Tsai
H M
HM
D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; D000328:Adult; D016026:Bone Marrow Transplantation / Q000009:adverse effects*; D003937:Diagnosis, Differential; D019281:Dimerization; D005260:Female; D006463:Hemolytic-Uremic Syndrome / Q000175:diagnosis / Q000209:etiology*; D006801:Humans; D007668:Kidney / Q000098:blood supply; D008297:Male; D008666:Metalloendopeptidases / Q000378:metabolism*; D008833:Microcirculation; D008875:Middle Aged; D011697:Purpura, Thrombotic Thrombocytopenic / Q000175:diagnosis / Q000209:etiology; D013577:Syndrome; D013927:Thrombosis; D014841:von Willebrand Factor / Q000378:metabolism*
D014841:von Willebrand Factor; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human