Thrombotisch-thrombozytopenische Purpura

Thrombotic-thrombocytopenic purpura (TTP) is a microangiopathic disorder characterized by multiple von Willebrand-Factor (vWF) rich microthrombi affecting the arterioles and capillary vessels of several organs. Ultra large von Willebrand multimers cause the blood clotting process by linking to platelets due to a lack of a plasma metalloprotease named ADAMTS13. Deficiency of this vWF-cleaving enzyme is caused by an inborn mutation in the gene coding or, more often, by acquired autoantibodies that inhibit ADAMTS13. TTP is a life-threatening disease which requires urgent admission to a hematological centre. Plasmapheresis therapy should be started immediately when diagnosis of primary TTP is likely. Patients typically present with schistozytes, hemolysis, thrombocytopenia and neurological abnormalities such as headache, focal deficits or coma. The monoclonal CD20 antibody rituximab targets ADAMTS13 antibody production and has the potential to be an effective therapy for relapsed TTP or initial treatment to shorten duration of plasma exchange.     

Rituximab provided long-term remission in a patient with severe thrombotic thrombocytopenic purpura refractory to plasma exchange

We report a patient with severe thrombotic thrombocytopenic purpura (TTP) refractory to plasmapheresis who was successfully treated with rituximab. A 57-year-old male patient was referred to our department for further differential diagnosis and treatment of anemia and severe thrombocytopenia. Progressive psychoneurotic symptoms, hemolytic anemia, thrombocytopenia, renal function insufficiency and fever led us to the diagnosis of TTP. ADAMTS13 activity was below 3% and an inhibitor for ADAMTS13 was detected. Treatment with plasmapheresis and high-dose steroid was initiated but without clinical benefit. Two weeks following the initiation of plasmapheresis, we decided to treat the patient with 7 cycles of rituximab. No severe rituximab-related adverse effects were observed. After treatment with rituximab, the disease remitted, and the ADAMTS13 activity level increased. The patient has remained in complete remission for more than 1 year. Our data suggest that rituximab may be the optimal immunosuppressive therapy for refractory thrombotic thrombocytopenic purpura caused by an anti-ADAMTS 13 inhibitor.     

Clinical usefulness of a functional assay for the von Willebrand factor cleaving protease (ADAMTS 13) and its inhibitor in a patient with thrombotic thrombocytopenic purpura

Decreased von Willebrand factor cleaving protease activity (VWFCP, ADAMTS 13) leads to persistence of unusually large multimers of von Willebrand factor that bind to platelets, causing platelet aggregates, microangiopathic hemolysis, and thrombocytopenia in patients with thrombotic thrombocytopenic purpura (TTP). The clinical value of measuring ADAMTS 13 and its inhibitor is not fully defined; the case reported here illustrates the usefulness of the assay to help confirm the clinical diagnosis in a patient with other potential causes for thrombotic microangiopathy; the assay also helped in making treatment decisions. A patient with systemic lupus erythematosis (SLE) presented with fever and abdominal pain, thrombocytopenia, and anemia. Thrombotic microangiopathy was diagnosed by the appearance of schistocytes, decreasing platelet count, and evidence of hemolysis. ADAMTS 13 was decreased and an inhibitor was demonstrated in the patient's initial blood sample within 24 hr of admission. Plasma exchange was initiated, and serial assays showed increased ADAMTS 13 activity and decreased inhibitor after each plasma exchange; there was a rebound in inhibitor and a decrease in ADAMTS 13 activity prior to the next exchange that lessened over time. Increasing levels of protease activity correlated with clinical and laboratory improvement. Measurement of ADAMTS 13 activity and its inhibitor aided in the diagnosis of this complicated case of a patient with other potential causes for microangiopathic hemolysis. Subsequent levels correlated with the clinical course, and disappearance of the inhibitor indicated that long-term plasma exchange or other immunosuppressive treatment was not needed.     

Efficacy of rituximab in acute refractory or chronic relapsing non-familial idiopathic thrombotic thrombocytopenic purpura: a systematic review with pooled data analysis

Idiopathic thrombotic thrombocytopenic purpura (TTP) occurs primarily due to the formation of autoantibody against ADAMTS13, a specific von Willebrand factor-cleaving protease, resulting in low ADAMTS13 activity and subsequent accumulation of large vWF multimers, platelet aggregation and thrombus formation in the microvasculature of tissues. Limited clinical data suggest that the administration of anti-CD20 antibody (rituximab) may be useful in treating acute refractory or chronic relapsing idiopathic TTP. We carried out a systematic review with pooled data analysis using individual patient data to evaluate the efficacy of rituximab in these settings. Fifteen case series and 16 case reports comprising 100 patients were eligible for the study. Median age was 39?years. Male constituted 31?% and female 69?%. Complete remission was seen in 98?%, non-response in 2?% and relapse after complete remission in 9?%. For patients with complete remission, median follow-up was 13?months. Median platelet recovery from the first dose of rituximab was 14?days. ADAMTS13 inhibitor positivity and severe ADAMTS13 deficiency were highly predictive of the response to rituximab, implying that these can be useful markers in predicting response to rituximab in acute refractory or chronic relapsing idiopathic TTP.     

Rituximab prevents recurrence of thrombotic thrombocytopenic purpura: a case report

Thrombotic thrombocytopenic purpura (TTP) is a rare disorder of small vessels that is associated with deficiency of the von Willebrand factor-cleaving protease, ADAMTS13. The presence of anti-ADAMTS13 autoantibodies is considered a factor predisposing to relapses. Despite close monitoring and intensive plasma treatment, in these patients acute episodes are still associated with substantial morbidity and mortality rates, and the optimal therapeutic option should be prevention of relapses. This study was conducted in a patient with recurrent TTP due to high titers of ADAMTS13 inhibitors, who used to have 2 relapses of TTP a year. The study compared the standard treatment plasma exchange with rituximab. Results documented that plasma exchange had only a small transient effect on ADAMTS13 activity and inhibitors; on the contrary, prophylaxis with rituximab was associated with disappearance of anti-ADAMTS13 antibodies, a progressive recovery of protease activity, and it allowed the patient to maintain a disease-free state during a more than 2-year follow-up.     

Rituximab for chronic recurring thrombotic thrombocytopenic purpura: a case report and review of the literature

Deficiency of von Willebrand factor (VWF) cleaving protease ADAMTS13 has been demonstrated to be the proximate cause of a subset of thrombotic microangiopathic haemolytic anaemias (MAHA) typical for thrombotic thrombocytopenic purpura (TTP). ADAMTS13 gene mutations cause the hereditary form; acquired deficiency has been attributed to presence of an autoantibody, which may represent a specific subset of MAHA best termed 'autoimmune thrombotic thrombocytopenic purpura'. We describe a patient with relapsing TTP because of ADAMTS13 inhibitors, who failed to achieve sustained remission despite therapies with plasma exchange, steroids, vincristine, staphylococcal protein A and splenectomy. The ADAMTS13 inhibitor titre remained elevated and clinical stability was only maintained by plasma exchange every 2-3 d over a period of 268 d. The patient then received rituximab therapy (eight doses of 375 mg/m2 weekly), during which she required five plasma exchanges in the first 10 d, two exchanges in the next 3 weeks, and none thereafter for 450 d and ongoing. The ADAMTS13 inhibitor titre decreased and enzyme activity increased. We compared this case with that of seven previously reported TTP cases also treated with rituximab; experience suggests that rituximab therapy deserves further investigation for patients with either refractory or relapsing TTP caused by ADAMTS13 inhibitors.     

Pathogenesis of thrombotic thrombocytopenic purpura: ADAMTS13 deficiency and beyond

Thrombotic thrombocytopenic purpura (TTP) is characterized by the systemic deposition of platelet thrombi with abundance of von Willebrand factor (vWF) in the arterioles and capillaries. Recently, vWF protease (ADAMTS13) activity was found to be severely deficient in hereditary TTP as well as acquired idiopathic TTP. Homozygous or compound heterozygous mutations of ADAMTS13 gene were demonstrated in hereditary TTP. Autoantibodies against ADAMTS13 were present in majority of patients with idiopathic TTP and ticlopidine- and clopidogrel-associated TTP. The deficiency of ADAMTS13 leaves unchecked the hyperadhesive vWF unfolded under high shear stress in the microvessels, resulting in the formation of platelet thrombi, which in turn causes TTP. ADAMTS13 activity is usually normal in hemolytic uremic syndrome. Approximately 0 to 67% of idiopathic TTP patients reported may not be severely deficient of ADAMTS13. Therefore, acquired TTP is not caused by ADAMTS13 deficiency alone and may be triggered by certain stimuli that possibly cause autoimmune reactivity to ADAMTS13, and also induce platelet aggregation either dependent on or independent of vWF, and/or vascular injury, to account for variable clinical and laboratory presentations. Plasma samples from TTP patients have been shown to induce endothelial cell apoptosis and activation. Platelet aggregating factors independent of vWF purified from the plasma of a subset of TTP patients have been reported and shown to be inhibited by normal plasma and immunoglobulin G purified from normal plasma. Defective fibrinolysis and abnormal natural coagulation inhibitors may enhance the thrombi formation in the microcirculation.     

Molecular mechanisms in thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is characterized by thrombocytopenia and microangiopathic hemolysis. Unlike the typical hemolytic uremic syndrome (HUS), which follows infection with shiga toxin-producing microorganisms, most cases of TTP do not have an obvious etiology. Recent studies revealed that a plasma zinc metalloprotease ADAMTS (a disintegrin and metalloprotease with thrombospondin type 1 motif) 13 cleaves von Willebrand factor in a shear-dependent manner. Deficiency of ADAMTS13, due to autoimmune inhibitors of the protease or genetic mutation in the ADAMTS13 gene, results in a propensity to the development of von Willebrand factor-platelet aggregation and intravascular thrombosis characteristic of TTP. The identification of the molecular defect in TTP raises the prospect that this hitherto mysterious disorder will be managed with a more rationally designed strategy in the near future.     

Presence of ADAMTS13 activity in a patient with metastatic cancer and thrombotic microangiopathy

Patients with metastatic cancers occasionally present with microangiopathic hemolysis and thrombocytopenia. A patient with metastatic adenocarcinoma of the colon and microangiopathic hemolysis was treated with plasma exchange for a presumptive diagnosis of thrombotic thrombocytopenic purpura (TTP). However, her condition continued to deteriorate and a determination of ADAMTS13 activity revealed that she did not have TTP. Despite similarity in clinical manifestation, microangiopathic hemolysis in patients with metastatic cancers may not be caused by ADAMTS13 deficiency and the role of plasma exchange in such patients should be reevaluated.     

Congenital thrombotic thrombocytopenic purpura caused by new compound heterozygous mutations of the ADAMTS13 gene

Upshaw–Schulman syndrome (USS) is due to severe congenital deficiency of von Willebrand factor (VWF)‐cleaving protease ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 domains, nr 13) activity resulting in the presence of unusually large forms of VWF in the circulation, causing intravascular platelet clumping and thrombotic microangiopathy. Our patient, a 26‐year‐old man, had attacks of thrombotic thrombocytopenic purpura (TTP) with thrombocytopenia and a urine dipstick positive for hemoglobin (4+), often as the only sign of hemolytic activity. He had ADAMTS13 activity of <1% of normal plasma without the presence of inhibitors of ADAMTS13. ADAMTS13 deficiency was caused by two new mutations of the ADAMTS13 gene: a deletion of a single nucleotide in exon17 (c. 2042 delA) leading to a frameshift (K681C fs X16), and a missense mutation in exon 25 (c.3368G>A) leading to p.R1123H. This case report confirms the importance of the analysis of the ADAMTS13 activity and its inhibitor in patients who have episodes of TTP, with a very low platelet count and sometimes without the classic biochemical signs of hemolysis.     

Two cases of refractory thrombotic thrombocytopenic purpura associated with collagen vascular disease were significantly improved by rituximab treatment

Thrombotic thrombocytopenic purpura (TTP) is a rare disorder of small vessels. TTP is associated with deficiency of the von Willebrand factor-cleaving protease, ADAMTS13, and its inhibitor. Low ADAMTS13 activity is present in most of idiopathic TTP patients. The prognosis of TTP was improved by plasma exchange treatment, which replaces the ADAMTS13 and removes ADAMTS13 inhibitor. However, ADAMTS13 activity is normal in some TTP patients. These are found among the secondary TTP patients associated with collagen disease, hematopoietic stem cell transplantation, malignancy, or drugs. In addition, most of them do not respond to plasma exchange. On the other hand, several reports demonstrated that rituximab, which is an anti-CD20 monoclonal antibody, is effective for refractory TTP cases caused by ADAMTS13 deficiency. It is considered that the effect of rituximab is associated with disappearance of ADAMTS13 inhibitor. However, rituximab therapy was effective for the TTP patients with normal ADAMTS13 activity in our cases. We considered another mechanism of rituximab for TTP cases.     

Pediatric thrombotic thrombocytopenic purpura

Child‐onset thrombotic thrombocytopenic purpura (TTP) is a rare entity of thrombotic microangiopathy (TMA). The pathophysiology of the disease is based on a severe functional deficiency of ADAMTS13 (activity <10%), the specific von Willebrand factor (VWF)‐cleavage protease. This deficiency may be either acquired (associated anti‐ADAMTS13 autoantibodies) or congenital (resulting from biallelic mutations of ADAMTS13 gene). ADAMTS13 deficiency is responsible for the accumulation of high molecular weight multimers of VWF and the formation of platelet thrombi in the microcirculation. Consequently, microangiopathic hemolytic anemia and consumption thrombocytopenia are associated with organ ischemia. The differential diagnosis with other TMAs, autoimmune cytopenias or hematological malignancies may be challenging. The exploration of ADAMTS13 (activity, antibodies, antigen, ADAMTS13 gene) supports the diagnosis of TTP. The first‐line treatment of the acute phase of TTP is based on plasmatherapy. In congenital TTP, patients with a chronic disease benefit from a prophylactic plasmatherapy. In autoimmune TTP, steroids and B‐cells depleting therapies increasingly are used together with plasma exchange. Long‐term follow‐up including the monitoring of ADAMTS13 activity is mandatory. A severe decrease in ADAMTS13 activity (<10%) may predict relapses and preemptive B‐cell depletion with rituximab can be used to prevent relapses.     

Effect of plasma exchange on plasma ADAMTS13 metalloprotease activity, inhibitor level, and clinical outcome in patients with idiopathic and nonidiopathic thrombotic thrombocytopenic purpura

Therapeutic plasma exchange is an effective empiric treatment for thrombotic thrombocytopenic purpura (TTP), but how therapy affects the level of a disintegrin and metalloprotease with thrombospondin type 1 motif 13 (ADAMTS13) or inhibitor has not been reported in many patients. We prospectively analyzed ADAMTS13 activity and inhibitor levels in 37 adults with TTP. ADAMTS13 level at presentation was lower than 5% in 16 of 20 patients with idiopathic TTP and in none of 17 patients with TTP associated with hematopoietic stem cell transplantation, cancer, drugs, or pregnancy (P <.00001). Seven of the 16 patients with ADAMTS13 activity lower than 5% ( approximately 44%) had inhibitors. For 8 patients followed serially with ADAMTS13 activity lower than 5% but no inhibitor at presentation, plasma exchange led to complete clinical remission and a rise in ADAMTS13 level. In contrast, 4 patients with low ADAMTS13 activity but high-titer inhibitor (> 5 units/mL) had neither a rise in ADAMTS13 activity nor a reduction in the inhibitor titer: 3 had recurrent disease and 1 died. Among 17 patients with AD-AMTS13 activity at presentation higher than 25%, 10 died. Mortality rate for idiopathic TTP was 15%, whereas mortality for nonidiopathic TTP was 59% (P <.02). We conclude that assays of ADAMTS13 activity and inhibitors in addition to the clinical categories (idiopathic TTP and nonidiopathic TTP) are predictive of outcome and may be useful to tailor patient treatment.     

Refractory thrombotic thrombocytopenic purpura successfully treated with a combination of rituximab and vincristine

A 26-year-old man was referred to our hospital with vomiting and high fever. He was disoriented and laboratory results showed microangiopathic hemolytic anemia (Hb 7.1 g/dl) and severe thrombocytopenia (15 x 10(3)/microl). The diagnosis of thrombotic thrombocytopenic purpura (TTP) was established. The activity of von Willebrand cleaving protease (ADAMTS13) was found to be remarkably low (<0.5%) and the high activity of the inhibitor (11.0 Bethesda U/ml) was detected, confirming the diagnosis of typical acquired TIP. Although he had been successfully treated with daily plasma exchange and methylprednisolone, he relapsed after a week. To this therapeutic strategy we added four weekly doses of rituximab (375 mg/m2) and two weekly doses of vincristine (1 mg/m2) simultaneously. The response was very rapid and complete, that is, the platelet count recovered to normal seven days after the first rituximab and vincristine treatment. The patient maintains complete remission nine months later under the administration of 17.5 mg prednisolone. Recovery of the plasma ADAMTS13 activity was clearly correlated with the decrease or disappearance of the inhibitor activity. Combination of rituximab and vincristine therapy would appear to be very effective against refractory TTP.     

Von Willebrand factor, ADAMTS13, and thrombotic thrombocytopenic purpura

Discoveries during the past decade have revolutionized our understanding of idiopathic thrombotic thrombocytopenic purpura (TTP). Most cases in adults are caused by acquired autoantibodies that inhibit ADAMTS13, a metalloprotease that cleaves von Willebrand factor within nascent platelet-rich thrombi to prevent hemolysis, thrombocytopenia, and tissue infarction. Although approximately 80% of patients respond to plasma exchange, which removes autoantibody and replenishes ADAMTS13, one third to one half of survivors develop refractory or relapsing disease. Intensive immunosuppressive therapy with rituximab appears to be effective as salvage therapy, and ongoing clinical trials should determine whether adjuvant rituximab with plasma exchange also is beneficial at first diagnosis. A major unanswered question is whether plasma exchange is effective for the subset of patients with idiopathic TTP who do not have severe ADAMTS13 deficiency.     

Von Willebrand factor-cleaving protease (ADAMTS13) in thrombocytopenic disorders: a severely deficient activity is specific for thrombotic thrombocytopenic purpura

A severe deficiency in von Willebrand factor-cleaving protease (ADAMTS13) activity (< 5% that in normal plasma) has been observed in most patients with a diagnosis of thrombotic thrombocytopenic purpura (TTP) but not in those with a diagnosis of hemolytic uremic syndrome. However, ADAMTS13 deficiency has been claimed not to be specific for TTP, since it was observed in various thrombocytopenic and other conditions. We studied 68 patients with thrombocytopenia due to severe sepsis or septic shock (n = 17), heparin-induced thrombocytopenia (n = 16), idiopathic thrombocytopenic purpura (n = 10), or other hematologic (n = 15) or miscellaneous conditions (n = 10). Twelve of the 68 patients had subnormal levels of ADAMTS13 activity (相似文献   

A perspective on the measurement of ADAMTS13 in thrombotic thrombocytopaenic purpura

The recent discovery of the von Willebrand Factor (vWF) cleaving protease (ADAMTS13) and the association of its deficiency with thrombotic thrombocytopaenic purpura (TTP) has generated both enormous interest and considerable confusion. Ultra large von Willebrand Factor (UL vWF) multimers are present in the plasmas of patients with chronic relapsing TTP in remission but disappear during an attack. This observation led to the recognition that UL vWF multimers precipitate the thrombotic occlusion of arterioles, a feature that characterizes TTP. Multiple mutations in ADAMTS13 are associated with congenital TTP and neutralizing autoantibodies have been demonstrated in the acquired TTP syndrome. Although a number of functional assays for this enzyme have been described, the more rigorously evaluated assays are difficult to perform outside a research laboratory. There is also an enduring uncertainty about the specificity of ADAMTS13 deficiency for the diagnosis of acquired TTP and a perception that the result does not alter patient management. The cloning of the ADAMTS13 gene has also raised the prospect of recombinant enzyme therapy for the treatment of TTP, and this has heightened the need for a simple assay. In this review, we evaluate the value of measuring this enzyme in the management of TTP.     

Rituximab therapy for refractory thrombotic thrombocytopenic purpura

While most patients of thrombotic thrombocytopenic purpura (TTP) respond to plasma exchange and achieve remission, a subset of the patients experience multiple relapses or develop a persistent disease that may be debilitating and life threatening. We report the experience of rituximab treatment in three consecutive patients who had required periodic plasma exchange for greater than 50-180 days after failing other modalities of treatments. Two patients each received eight doses of rituximab infusion and had clinical remissions that have lasted for 23 months and ongoing in one patient and for 17 months before relapse in the other. The third patient received four doses of rituximab infusion and had improvement of disease for 60 days until her death from unrelated causes. Analysis of the von Willebrand factor-cleaving metalloprotease activity (ADAMTS13) and its inhibitor in two patients showed that rituximab treatment was associated with a rise of the protease level and a decrease of the inhibitor titers in one patient who achieved clinical remission and a decrease of the inhibitor titer but no increase in protease level in the other patient who had a partial response. Based on the responses to rituximab and its mild toxicity in these three patients, and the lack of effective alternative treatments, additional exploration of the role of rituximab in the treatment of refractory TTP is warranted.     

A case of mixed connective tissue disease complicated with thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a rare complication of mixed connective tissue disease (MCTD). In this report, we describe the case of a 73-year-old Japanese woman with MCTD who developed fever, thrombocytopenia, and microangiopathic hemolytic anemia and was diagnosed with MCTD together with TTP. The activity of von Willebrand factor (vWF) cleaving metalloprotease ADAMTS13 was low and considered to have contributed to the disease activity of TTP. The patient died despite intensive treatment of plasma exchange (PEX) and steroid pulse therapy. Autopsy results revealed that the kidneys had platelet and fibrin thrombi, which occluded capillaries and arterioles. These findings were compatible with TTP and the decreased activity of ADAMTS13 was considered to be associated with the disease activity of TTP.     

Thrombocytopenic purpura and cardiomyopathy in pregnancy reversed by combined plasma exchange and infusion

Thrombocytopenia and hemolytic anemia have been seen with thrombotic thrombocytopenic purpura (TTP), HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets), and hemolytic uremic syndrome (HUS). Differentiating between TTP, HUS, and HELLP syndrome is often difficult. Coexistence of TTP and HELLP is possible. Cardiomyopathy occurring in pregnancy can be idiopathic or associated with TTP. We describe a previously healthy woman who developed thrombocytopenia and hemolysis at 34 wk gestation. The patient underwent delivery after transfusion with platelets and RBCs. The suspicion of TTP was raised, and plasma exchange was begun by the third hospital day. On the seventh day of treatment, the patient developed shortness of breath, and an echocardiogram showed global hypokinesis with an ejection fraction of 25%. Plasma infusion, one unit q 4 h, was initiated in addition to the daily plasma exchange. The patient improved and her ejection fraction normalized. Plasma exchange and infusion and corticosteroids were gradually tapered off. von Willebrand factor (vWF) protease activity in the plasma upon transfer was completely deficient with the presence of inhibitor. This case illustrates that vWF protease assay and detection of inhibitor can be used for the diagnosis of TTP during pregnancy; and a severe cardiomyopathy in TTP can be reversed rapidly with combined plasma exchange and infusion.