von Willebrand factor cleaving protease (ADAMTS-13) and ADAMTS-13 neutralizing autoantibodies in 100 patients with thrombotic thrombocytopenic purpura

Authors

  • Flora Peyvandi,

    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, IRCCS Maggiore Hospital and University of Milano, Milan, Italy
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  • Silvia Ferrari,

    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, IRCCS Maggiore Hospital and University of Milano, Milan, Italy
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  • Silvia Lavoretano,

    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, IRCCS Maggiore Hospital and University of Milano, Milan, Italy
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  • Maria Teresa Canciani,

    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, IRCCS Maggiore Hospital and University of Milano, Milan, Italy
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  • Pier Mannuccio Mannucci

    1. Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, IRCCS Maggiore Hospital and University of Milano, Milan, Italy
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Pier Mannuccio Mannucci, Via Pace 9, 20122 Milan, Italy.
E-mail: piermannuccio.mannucci@unimi.it

Summary

The congenital or acquired deficiency of the von Willebrand factor (VWF) cleaving protease, ADAMTS-13 has been specifically associated with a diagnosis of thrombotic thrombocytopenic purpura (TTP), a microangiopathy characterized by the formation of occlusive platelet thrombi. The mechanisms of TTP were investigated in 100 patients diagnosed on the basis of the presence of at least three of the following: thrombocytopenia, haemolytic anaemia, elevated serum levels of lactate dehydrogenase and neurological symptoms. Plasma levels of ADAMTS-13 were severely reduced (<10% of normal) in 48%, moderately reduced (between 10% and 46%) in 24% and normal (>46%) in 28%. A neutralizing antibody was the cause of the deficiency in 38% of the cases, with a higher prevalence of this mechanism (87%) in the 48 patients with severely reduced ADAMTS-13. Double heterozygosity for a 29 base pair (bp) deletion and a nucleotide insertion and homozygosity for a 6 bp deletion in the ADAMTS13 gene were identified only in two patients born from consanguineous marriages. In conclusion, this study indicated that ADAMTS-13 was normal in nearly one-third of patients with TTP and that ADAMTS-13 deficiency was not associated with the presence of neutralizing antibodies in more than half of the patients.

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