Furlan M, Robles R, Galbusera M, Remuzzi G, Kyrle P A, Brenner B, Krause M, Scharrer I, Aumann V, Mittler U, Solenthaler M, Lämmle B
Central Hematology Laboratory, University Hospital, Bern, Switzerland.
N Engl J Med. 1998 Nov 26;339(22):1578-84. doi: 10.1056/NEJM199811263392202.
Thrombotic thrombocytopenic purpura and the hemolytic-uremic syndrome are severe microvascular disorders of platelet clumping with similar signs and symptoms. Unusually large multimers of von Willebrand factor, capable of agglutinating circulating platelets under high shear stress, occur in the two conditions. We investigated the prevalence of von Willebrand factor-cleaving protease deficiency in patients with familial and nonfamilial forms of these disorders.
Plasma samples were obtained from 53 patients with thrombotic thrombocytopenic purpura or hemolytic-uremic syndrome. Von Willebrand factor-cleaving protease was assayed in diluted plasma samples with purified normal von Willebrand factor as the substrate. The extent of the degradation of von Willebrand factor was assessed by electrophoresis in sodium dodecyl sulfate-agarose gels and immunoblotting. To determine whether an inhibitor of von Willebrand factor-cleaving protease was present, we measured the protease activity in normal plasma after incubation with plasma from the patients.
We examined 30 patients with thrombotic thrombocytopenic purpura and 23 patients with the hemolytic-uremic syndrome. Of 24 patients with nonfamilial thrombotic thrombocytopenic purpura, 20 had severe and 4 had moderate protease deficiency during an acute event. An inhibitor found in 20 of these patients was shown to be IgG in five of five tested plasma samples. Of 13 patients with nonfamilial hemolytic-uremic syndrome, 11 had normal levels of activity of von Willebrand factor-cleaving protease during the acute episode, whereas in 2 patients, the activity was slightly decreased. All 6 patients with familial thrombotic thrombocytopenic purpura lacked von Willebrand factor-cleaving protease activity but had no inhibitor, whereas all 10 patients with familial hemolytic-uremic syndrome had normal protease activity. In vitro proteolytic degradation of von Willebrand factor by the protease was studied in 5 patients with familial and 7 patients with nonfamilial hemolytic-uremic syndrome and was normal in all 12 patients.
Nonfamilial thrombotic thrombocytopenic purpura is due to an inhibitor of von Willebrand factor-cleaving protease, whereas the familial form seems to be caused by a constitutional deficiency of the protease. Patients with the hemolyticuremic syndrome do not have a deficiency of von Willebrand factor-cleaving protease or a defect in von Willebrand factor that leads to its resistance to protease.
血栓性血小板减少性紫癜和溶血尿毒综合征是伴有相似体征和症状的血小板聚集性严重微血管疾病。在这两种疾病中会出现异常大的血管性血友病因子多聚体，其在高剪切应力下能够凝集循环中的血小板。我们调查了这些疾病的家族性和非家族性形式患者中血管性血友病因子裂解蛋白酶缺乏的患病率。
从53例血栓性血小板减少性紫癜或溶血尿毒综合征患者中获取血浆样本。以纯化的正常血管性血友病因子为底物，在稀释的血浆样本中检测血管性血友病因子裂解蛋白酶。通过十二烷基硫酸钠 - 琼脂糖凝胶电泳和免疫印迹评估血管性血友病因子的降解程度。为了确定是否存在血管性血友病因子裂解蛋白酶的抑制剂，我们在将患者血浆与正常血浆孵育后测量蛋白酶活性。
我们检查了30例血栓性血小板减少性紫癜患者和23例溶血尿毒综合征患者。在24例非家族性血栓性血小板减少性紫癜患者中，20例在急性发作时有严重的蛋白酶缺乏，4例有中度蛋白酶缺乏。在这些患者中的20例中发现的一种抑制剂在5份检测血浆样本中的5份中被证明是IgG。在13例非家族性溶血尿毒综合征患者中，11例在急性发作期间血管性血友病因子裂解蛋白酶活性水平正常，而在2例患者中，活性略有降低。所有6例家族性血栓性血小板减少性紫癜患者均缺乏血管性血友病因子裂解蛋白酶活性，但无抑制剂，而所有10例家族性溶血尿毒综合征患者的蛋白酶活性均正常。在5例家族性和7例非家族性溶血尿毒综合征患者中研究了蛋白酶对血管性血友病因子的体外蛋白水解降解，所有12例患者均正常。
非家族性血栓性血小板减少性紫癜是由于血管性血友病因子裂解蛋白酶的抑制剂所致，而家族性形式似乎是由蛋白酶的先天性缺乏引起的。溶血尿毒综合征患者不存在血管性血友病因子裂解蛋白酶缺乏或血管性血友病因子中导致其对蛋白酶产生抗性的缺陷。
