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Summary: Congenital thrombotic thrombocytopenic purpura (cTTP), known as Upshaw–Schulman syndrome, is an ultrarare thrombotic disorder caused by ADAMTS13 gene mutations; however, its long‐term outcomes have not been widely studied. A questionnaire survey was administered to physicians of patients in the Japanese cTTP registry to characterise these outcomes. We analysed 55 patients in remission, with 41 cases receiving prophylactic fresh frozen plasma (FFP; median dosage: 13·2 ml/kg per month) and 14 receiving on‐demand FFP. Patients receiving prophylactic FFP were considered as having a more severe form of the disease and had lower platelet counts and higher serum creatinine levels than those receiving on‐demand FFP (median 138 × 109/l vs. 243 × 109/l, P = 0·003 and 0·71 mg/dl vs 0·58 mg/dl, P = 0·009, respectively). Patients who received prophylactic FFP more commonly developed organ damage, including renal impairment, cerebral infarctions, and cardiac hypofunction, than those who did not. Adverse FFP‐related events were seen in 78% of the prophylactic FFP group, with allergic reactions being most common. Since current protocols for FFP administration to the prophylactic FFP group in Japan may be insufficient for preventing cumulative organ damage, a higher dosage of ADAMTS13 supply using recombinant ADAMTS13 agent is needed in these patients. [ABSTRACT FROM AUTHOR]

Background: Platelet (PLT) transfusions are probably harmful in patients with acquired idiopathic thrombotic thrombocytopenic purpura (aTTP). Introduction of a rapid assay for ADAMTS13 activity should reduce the time to definite diagnosis of aTTP, reduce the amount of inappropriately transfused PLT concentrates, and improve mortality and morbidity.Study Design and Methods: We selected 265 aTTP patients with severe ADAMTS13 deficiency. Of these, 91 patients were diagnosed by March 2005 (Period 1), when ADAMTS13 activity was measured by von Willebrand factor multimer assay, which took 4 to 7 days until the result was reported. An additional 174 patients were diagnosed after April 2005 (Period 2), when the activity was measured by a chromogenic enzyme-linked immunosorbent assay, which took 1 to 2 days.Results: We found no significant differences in 30-day survival rate between the two periods. Overall, 48 patients received PLT transfusions. Mortality was slightly greater between patients with (22.9%) versus without PLT transfusion (17.7%), but not significant. In Period 1, Cox proportional hazards regression analysis showed that older age (≥60 years) and PLT transfusion administration were independent factors associated with higher risks of 30-day mortality. In contrast, in Period 2, lower Rose-Eldor TTP severity score and use of plasma exchange and corticosteroid therapy were independent factors associated with higher survival rates while nonadministration of PLT transfusions was not.Conclusion: Our results indicate that PLT transfusions are harmful for aTTP patients when the definite diagnosis of severe ADAMTS13 deficiency is delayed. If it can be done as soon as possible, PLT transfusions for severe bleeding or surgical interventions might be allowed with subsequent plasmapheresis. [ABSTRACT FROM AUTHOR]

A 31-year-old pregnant woman was transferred to the emergency room at 27 weeks of gestation. She had one-day history of fever and upper abdominal pain. Soon after admission, she underwent cardiopulmonary arrest. Autopsy was performed and multiple microthrombi were seen within the small-caliber vessels of many organs, but not in the lungs. Immunohistochemical staining revealed that the thrombi were rich in von Willebrand factor. We also obtained results which showed severely deficient plasma a disintegrin-like and metalloprotease with thrombospondin motifs (ADAMTS) 13 activity and positive ADAMTS13 inhibitor, confirming a diagnosis of thrombotic thrombocytopenic purpura. As far as we know, in Japan, this is the first autopsy report of sudden maternal death from thrombotic thrombocytopenic purpura. We expect that the routine laboratory application of ADAMTS13 assays for unknown thrombocytopenic patients during pregnancy may help in differential diagnosis at an earlier stage of the disease and facilitate tailor-made therapeutic intervention. [ABSTRACT FROM AUTHOR]

Upshaw–Schulman syndrome (USS) is a congenital thrombotic thrombocytopenic purpura (TTP) due to mutations in the gene that encodes for ADAMTS13 ( ADAMTS13), but its clinical signs may be mild or absent during childhood. We have identified 37 patients with USS (24 females, 13 males) belonging to 32 families. The nine women from six families who were diagnosed during their first pregnancy are the focus of this report. Six of the nine women had episodes of thrombocytopenia during childhood misdiagnosed as idiopathic thrombocytopenic purpura. Thrombocytopenia occurred during the second–third trimesters in each of their 15 pregnancies, with 16 babies (one twin pregnancy), often followed by TTP. Of 15 pregnancies, eight babies were stillborn or died soon after birth, and the remaining seven were all premature except one, who was born naturally following plasma infusions to the mother that had started at 8 weeks’ gestation. All nine USS women had severely deficient ADAMTS13 activity. ADAMTS13 analyses demonstrated that eight women were compound heterozygotes of Y304C/G525D (2 siblings), R125VfsX6/Q1302X (2 siblings), R193W/R349C (2 siblings), I178T/Q929X, and R193W/A606P; one woman was homozygous for R193W. Only the R193W mutation has been previously reported. These observations emphasize the importance of measuring ADAMTS13 activity in the evaluation of thrombocytopenia during childhood and pregnancy. [ABSTRACT FROM AUTHOR]

Background: In 2013, eculizumab was approved for treatment of the atypical hemolytic-uremic syndrome (aHUS) in Japan, which was defined as a thrombotic microangiopathy (TMA) excluding Shiga toxin-producing Escherichia coli-HUS and thrombotic thrombocytopenic purpura. Simultaneously, post-marketing surveillance was started to assess its safety and effectiveness. In 2016, Japanese clinical guide redefined terms to limit the use of "aHUS" to complement-mediated HUS only. Accordingly, TMA with other causes was defined as secondary TMA. Here we report the interim analysis of post-marketing surveillance of pediatric patients with aHUS and secondary TMA.Methods: Pediatric patients treated with eculizumab from approval to 15 March 2017 were included in this observational real-world study. Clinical endpoints of effectiveness were TMA event-free status, complete TMA response, platelet count normalization, and improvement of estimated glomerular filtration rate (eGFR). Adverse reactions to eculizumab were also analyzed.Results: In 27 pediatric patients with aHUS, median age at diagnosis was 4 years. Complement genes' variants were detected in 14 of 21 patients (66.7%). Median time from diagnosis to eculizumab initiation was 2.0 days. TMA event-free status, complete TMA response, platelet normalization, and improvement in eGFR were achieved in 85.2, 36.4, 78.3, and 75.0% of patients, respectively. Three patients with aHUS died. Twenty-four and 10 adverse reactions were reported in 31 aHUS patients and 17 secondary TMA patients, respectively; however, no eculizumab-related death or meningococcal infection was reported.Conclusions: This interim analysis confirmed that eculizumab is well-tolerated and effective for Japanese pediatric patients with aHUS in a real-world setting. [ABSTRACT FROM AUTHOR]

Background: Eculizumab has been available for the treatment of atypical hemolytic-uremic syndrome (aHUS) in Japan since 2013. To assess safety and effectiveness of eculizumab in adult aHUS patients in the real-life setting, we performed interim analysis of a post-marketing surveillance mandated by Japanese regulations.Methods: This study enrolled any patient who was diagnosed with TMA excluding Shiga toxin-producing Escherichia coli-HUS or thrombotic thrombocytopenic purpura based on Japanese clinical guide published in 2013 as inclusion criteria and treated with eculizumab. Although the term aHUS was redefined to denote only complement-mediated HUS in the guide revised in 2016, the patients with TMA caused by other causes (secondary TMA) were included. Patient outcomes and safety were evaluated at 6 months, 12 months, and annually thereafter.Results: Thirty-three patients with aHUS and 27 patients with secondary TMA were enrolled. Median treatment duration of aHUS was 24weeks. Complement genes variants were detected in 11 of 18 patients with aHUS (61.1%). Among the 29 aHUS patients with available baseline data, platelet count (PLT), lactic dehydrogenase and serum creatinine (SCr) improved within 1-month after eculizumab initiation. TMA event-free status, complete TMA response, PLT normalization, and SCr decrease were achieved in 67.9% (19/28), 27.8% (5/18), 56.5% (13/23), and 57.1% (16/28) of patients, respectively. Thirty-three and 11 adverse reactions were observed in patients with aHUS (13/33 patients) and secondary TMA (6/27 patients), respectively.Conclusions: This interim analysis confirmed the acceptable safety profile and effectiveness of eculizumab for Japanese adult aHUS patients in real-world settings. [ABSTRACT FROM AUTHOR]

Upshaw-Schulman syndrome (USS) is a thrombo-hemorrhagic disease caused by congenital deficiency of ADAMTS13 due to ADAMTS13 gene mutations. USS is characterized by repeated episodes of thrombocytopenia and microangiopathic hemolytic anemia that respond dramatically to infusions of fresh frozen plasma. There are two phenotypic expressions of USS: one is the early-onset type and the other, the late-onset type, is asymptomatic during childhood with the first bout of thrombotic thrombocytopenic purpura (TTP) developing after adolescence or during adulthood. We found that gravida with the latter phenotype developed thrombocytopenia and hemolytic anemia during the second or third trimesters, often followed by thrombotic microangiopathies (TMAs). These phenomena suggest that elevated plasma von Willebrand Factor (VWF) might be crucial because plasma levels of VWF antigen usually increase by 200–500% during this period of gestation. Here, we performed platelet function assays using a mixture of anti-coagulated blood from normal volunteers, human VWF, anti-ADAMTS13 monoclonal antibody A10, and purified plasma-derived ADAMTS13 to investigate the effect of plasma VWF levels on platelet thrombus formation in the context of deficient ADAMTS13. In vitro studies showed that mural thrombus formation and platelet aggregation under high shear stress were markedly augmented by increasing the amounts of exogenously added VWF when ADAMTS13 activity was deficient, as may be the case in the in vivo circulation of gravida with USS. These results suggest that highly elevated plasma VWF might accelerate platelet thrombus formation not only in the circulation but also on the surface of vascular endothelial cells in the setting of ADAMTS13 deficiency in USS. [ABSTRACT FROM AUTHOR]

Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. In 2013, we developed diagnostic criteria to enable early diagnosis and timely initiation of appropriate treatment for aHUS. Recent clinical and molecular findings have resulted in several proposed classifications and definitions of thrombotic microangiopathy and aHUS. Based on recent advances in this field and the emerging international consensus to exclude secondary TMAs from the definition of aHUS, we have redefined aHUS and proposed diagnostic algorithms, differential diagnosis, and therapeutic strategies for aHUS. [ABSTRACT FROM AUTHOR]

Abstract Upshaw-Schulman syndrome (USS) is an inherited type of thrombotic thrombocytopenic purpura (TTP) that is extremely rare, but often diagnosed during pregnancy. Reversible cerebral vasoconstriction syndrome (RCVS) is the transient stenosis of several cerebral arteries that is frequently diagnosed post-partum. We describe a 28-year-old woman with USS complicated by RCVS after delivery that was treated by plasma exchange with a good outcome. She was referred to our hospital with thunderclap headache, anemia and thrombocytopenia that occurred immediately postpartum. She was diagnosed with TTP and multiple cerebral infarctions. Plasma exchange promptly improved her symptoms on hospital day 3. Moreover, multiple stenoses of cerebral arteries indicating RCVS were resolved. Since her sister also had an episode of thrombocytopenia during pregnancy, inherited TTP was suspected and genetic analyses confirmed USS. Pregnancy is a risk for not only TTP, but also RCVS. Endothelial damage might be an underlining cause and vasospasm after delivery is a trigger of RCVS. Plasma exchange was effective against both TTP and RCVS. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented on a rapid, fully automated and highly sensitive immunoassay for activity of ADAMTS13, a disintegrin and metalloprotease with thrombospondin type 1 motifs 13.

Background: Plasma exchange (PE) is the first-line treatment for primary acquired thrombotic thrombocytopenic purpura (aTTP) with severe deficiency of ADAMTS13 activity (ADAMTS13:AC). Some patients are poor responders to PE, raising concern over multiple pathogenetic pathways. Study Design and Methods: Based on 52 aTTP patients in our national cohort study, we monitored plasma levels of ADAMTS13, clinical and laboratory findings, and outcomes. In a representative poor responder to PE, we examined an ADAMTS13 inhibitor (ADAMTS13:INH) complex in plasma milieu, by means of a large-pore isoelectric focusing (IEF) analysis. Results: Of 52 aTTP patients, 20 were good responders and 32 were poor responders. In the latter group, plasma ADAMTS13:AC levels never increased to more than 10% of normal during 14 days after PE initiation. Mean (±SD) plasma ADAMTS13:INH titers (Bethesda unit/mL) were 5.7 (±4.5) before PE, but decreased to 1.4 (±0.8) on the fourth PE day and then remarkably increased to 14.8 (±10.0) on the 10th PE day, termed "inhibitor boosting," and then slowly decreased to undetectable level over 1 month. On admission, none of the routinely available clinical and laboratory markers differentiated these two groups. However, elevated pre-PE levels of ADAMTS13:INH were correlated with a poor response. We visualized an ADAMTS13:INH (immunoglobulin G) complex in a patient plasma by an IEF analysis and found proteolytic fragment of ADAMTS13 antigen by a two-dimensional IEF and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Conclusion: Findings from this cohort of aTTP patients demonstrated that inhibitor boosting often occurs in aTTP patients in Japan. Poor responders could be predicted by elevated pre-PE ADAMTS13:INH levels on admission, but not by routinely collected clinical or laboratory data. [ABSTRACT FROM AUTHOR]

Direct sequencing is a popular method to discover mutations in candidate genes responsible for hereditary diseases. A certain type of mutation, however, can be missed by the method. Here, we report a comprehensive genomic quantitative polymerase chain reaction ( qPCR) to complement the weakness of direct sequencing. Upshaw- Schulman syndrome ( USS) is a recessively inherited disease associated with severe deficiency of plasma ADAMTS13 activity. We previously analyzed ADAMTS13 in 47 USS patients using direct sequencing, and 44 of them had either homozygous or compound heterozygous mutations. Then, we sought to reveal more extensive defects of ADAMTS13 in the remaining three patients. We quantified copy numbers of each ADAMTS13 exon in the patients by using genomic qPCR. Each primer pair was designed to contain at least one of the two primers used in direct sequencing, to avoid missing any exonic deletions. The qPCR demonstrated heterozygous loss of exons 7 and 8 in one patient and exon 27 in the other, and further analysis revealed c.746_987+373del1782 and c.3751_3892+587del729, respectively. Genomic qPCR provides an effective method for identifying extensive defects of the target genes. [ABSTRACT FROM AUTHOR]

Atypical hemolytic uremic syndrome (aHUS) is rare and comprises the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Recently, abnormalities in the mechanisms underlying complement regulation have been focused upon as causes of aHUS. The prognosis for patients who present with aHUS is very poor, with the first aHUS attack being associated with a mortality rate of ~25 %, and with ~50 % of cases resulting in end-stage renal disease requiring dialysis. If treatment is delayed, there is a high risk of this syndrome progressing to renal failure. Therefore, we have developed diagnostic criteria for aHUS to enable its early diagnosis and to facilitate the timely initiation of appropriate treatment. We hope these diagnostic criteria will be disseminated to as many clinicians as possible and that they will be used widely. [ABSTRACT FROM AUTHOR]

Background Thrombotic thrombocytopenic purpura ( TTP) is characterized by deficient ADAMTS13 activity. Treatment involves plasma exchange ( PE). Both fresh-frozen plasma ( FFP) and cryosupernatant ( CSP) are used, but it remains to be determined which is more effective. Study Design and Methods To analyze the interaction between von Willebrand factor ( VWF) and ADAMTS13, we used large-pore isoelectric focusing ( IEF) analysis followed by detection with anti- ADAMTS13 monoclonal antibody. FFP, CSP, cryoprecipitate ( CP), and purified ADAMTS13 were analyzed for their effects on high shear stress-induced platelet aggregation ( H- SIPA). Results IEF analysis of normal plasma revealed three groups of ADAMTS13 bands with pI of 4.9 to 5.6, 5.8 to 6.7, and 7.0 or 7.5. Two band groups ( pI 4.9-5.6 and 5.8-6.7) were found in plasma of a patient with Type 3 von Willebrand disease, in which VWF is absent, whereas no bands were found in plasma of a patient with congenital ADAMTS13 deficiency. Mixing these plasmas generated the bands at pI 7.0 or 7.5, representing the VWF- ADAMTS13 complex; these bands were absent in CSP. FFP and purified ADAMTS13 down regulated H- SIPA in a dose-dependent manner. However, CP did not inhibit H- SIPA in the initial phase, and the degree of inhibition at the endpoint was almost indistinguishable from those of the other two plasma products. Conclusion Both plasma products ( FFP and CSP) are effective for PE in TTP patients. However, CSP may be more favorable, because it has lower levels of VWF and almost normal ADAMTS13 activity, but lower levels of ADAMTS13 in complex with larger VWF multimers. [ABSTRACT FROM AUTHOR]

Thrombotic thrombocytopenic purpura ( TTP) has not yet been reported to be associated with mutations in the Wiskott- Aldrich syndrome ( WAS) gene. WAS is an X-linked recessive disorder characterized by thrombocytopenia, small platelet size, eczema, recurrent infections, and increased risk of autoimmune disorders and malignancies. A broad spectrum of mutations in the WAS protein ( WASP) gene have been identified as causing the disease. In this study, we report on a 2-month-old Japanese boy who presented with cytomegalovirus ( CMV) infection and TTP. The activity of von Willebrand factor cleaving metalloproteinase, ADAMTS13 was low and the antibody against ADAMTS13 was positive (3.6 Bethesda U/mL). Although TTP was improved by plasma exchange and steroid pulse therapy, thrombocytopenia persisted and regular transfusions of irradiated platelets were needed. Tiny platelets were found on a peripheral blood smear. CMV genome was positive in peripheral blood by polymerase chain reaction and the CMV viremia continued to persist despite intravenous gancyclovir therapy. Through direct sequencing of genomic DNA of the WASP gene in the patient, we identified a novel mutation of WASP gene: the seventh nucleotide in exon 11 ( G) had been deleted (1345del G). This mutation causes a frameshift and a stop codon at amino acid 470. Western blotting demonstrated a truncated WAS protein. To our knowledge, this is the first report describing TTP in WAS patients with novel mutation in the WASP gene. [ABSTRACT FROM AUTHOR]

Abstract: Cilostazol is an anti-platelet drug that reversibly inhibits phosphodiesterase III (PDE-III), which is ubiquitously expressed in platelets and various tissues. PDE-III converts cyclic adenosine monophosphate (cAMP) to 5''-AMP and up-regulates the intracellular concentration of cAMP, a potent inhibitor of platelet aggregation. Unlike other anti-platelet drugs, cilostazol is unique because patients receiving this drug do not have a significantly prolonged bleeding time, but the reasons for this difference are still unknown. In this study, we have examined how cilostazol inhibits platelet thrombus formation using anti-coagulated normal whole blood in which the platelets were labeled with a fluorescent dye in comparison with the anti-GPIIb/IIIa agent, tirofiban. We used an in vitro assay to examine mural platelet thrombus growth on a collagen surface under a high-shear rate flow in the absence of ADAMTS13 activity. These experimental conditions mimic the blood flow in patients with thrombotic thrombocytopenic purpura. Using this model, we clearly determined that cilostazol down-regulates the height of mural platelet thrombi formed on a collagen surface in a dose-dependent manner, without affecting the surface coverage. The concentration of cilostazol used in this study was relatively high (60–120μM) compared to clinically relevant concentrations (1–3μM), which may be due to the in vivo synergistic effects of PDE-III present in other tissues aside from platelets. Cilostazol does not affect the initial formation of platelet thrombi, but does inhibit the height of thrombi. These results showed a sharp contrast to tirofiban, and address why cilostazol does not significantly prolong bleeding time, despite its strong anti-platelet activity. [Copyright &y& Elsevier]

Thrombotic thrombocytopenic purpura (TTP) is a type of thrombotic microangiopathy (TMA). Studies report that the majority of TTP patients present with a deficiency of ADAMTS13 activity. In a database of TMA patients in Japan identified between 1998 and 2008, 186 patients with first onset of acquired idiopathic (ai) ADAMTS13-deficient TTP (ADAMTS13 activity <5%) were diagnosed. The median age of onset of TTP in this group of patients was 54 years, 54.8% were female, 75.8% had renal involvement, 79.0% had neurologic symptoms, and 97.8% had detectable inhibitors to ADAMTS13 activity. Younger patients were less likely to present with renal or neurologic dysfunction (p<0.01), while older patients were more likely to die during the TTP hospitalization (p<0.05). Findings from this cohort in Japan differ from those reported previously from the United States, Europe, and Korea with respect to age at onset (two decades younger in the other cohort) and gender composition (60% to 100% female in the other cohort). We conclude that in one of the largest cohorts of ai-TTP with severe deficiency of ADAMTS13 activity reported to date, demographic characteristics differ in Japanese patients relative to those reported from a large Caucasian registry from Western societies. Additional studies exploring these findings are needed. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Autoantibodies to ADAMTS13 have a pivotal role in the pathogenesis of acquired thrombotic thrombocytopenic purpura (TTP). By decreasing the function of ADAMTS13, autoantibodies impair the cleavage of ultra-large von Willebrand factor (UL-VWF) multimers into smaller sizes, leading to lethal platelet-VWF thrombi in the microcirculation. We therefore aimed to determine the sites of autoantibody recognition on ADAMTS13. Materials and Methods: In this study, IgG purified from 13 acquired TTP patients were examined to determine their binding sites on ADAMTS13. Immobilized IgG on microtiter plate or proteinG beads was screened by phage library expressing various peptides of ADAMTS13. Results: In screening, diverse peptide sequences were obtained from almost all of the ADAMTS13 domains, including the spacer domain, which is considered a major binding site. In particular, we detected an identical amino-acid sequence in the C-terminus of the spacer domain from Gly662 to Val687 that was recognized by autoantibodies from 5 TTP patients. The specific autoantibody was expected to be associated with the plasma levels of the ADAMTS13 antigen or activity, and with the quantity of ADAMTS13 autoantibodies or the inhibitory autoantibody titer in TTP patient plasma. These measurements, however, did not seem to be related to the presence or absence of the specific autoantibody. Conclusions: These findings indicate that the specific autoantibody might be a feature of acquired TTP, although its clinical significance remains to be elucidated. [Copyright &y& Elsevier]

ADAMTS13 is a metalloproteinase that specifically cleaves unusually large von Willbrand factor multimers under high-shear stress. Deficiency of ADAMTS13 activity induces a life-threatening generalized disease, thrombotic thrombocytopenic purpura. We established a simple and efficient method to purify plasma ADAMTS13 (pADAMTS13) from cryosupernatant using an anti-ADAMTS13 monoclonal antibody (A10) that recognizes a conformational epitope within the disintegrin-like domain. Using the purified pADAMTS13, the amino acid residues involved in cleavage by thrombin, plasmin and leucocyte elastase were determined, and the carbohydrate moieties of this enzyme was analysed by lectin blots. Purified pADAMTS13 had a specific activity of 300 U/mg (25,057-fold purification) and the pI was 5.1–5.5. Cleavage sites of the purified pADAMTS13 by three proteases were identified; thrombin cleaved the four peptidyl bonds between Arg257–Ala258, Arg459–Ser460, Arg888–Thr889 and Arg1176–Arg1177, plasmin cleaved the three peptidyl bonds between Arg257–Ala258, Arg888–Thr889 and Arg1176–Arg1177, and elastase cleaved the two peptidyl bonds between Ile380–Ala381 and Thr874–Ser875. Lectin blot analysis indicated the presence of non-reducing terminal α2–6 and α2–3-linked sialic acid residues with penultimate β-galactose residues on the N- and O-linked sugar chains of pADAMTS13, suggesting that pADAMTS13 is cleared from the circulation via the hepatic asialoglycoprotein receptor like other plasma glycoproteins. [ABSTRACT FROM PUBLISHER]

Abstract: Introduction: Thrombotic microangiopathy (TMA) is a complication occurring after liver transplantation (LT), and an unusually large multimer (ULM) of Von Willebrand factor (VWF) and ADAMTS13 may play an important role in the onset of TMA during LT. Material and Methods: Eight-one patients underwent living donor LT (LDLT). Seventeen of those patients had both severe thrombocytopenia and hemolytic anemia with fragmented red cells and were diagnosed as TMA- like syndrome (TMALS). Results and Conclusions: A significant reduction of ADAMTS13 and an increase of VWF were observed in the patients with TMALS. The ADAMTS13 activity in patients after LDLT was significantly reduced from day 1 to day 21, and it was significantly low in those with TMALS at day 14 and 28. The VWF levels in patients with LDLT were significantly high, and the VWF/ADAMTS13 ratio was significantly increased in patients at 7, 14 and 28 days after LDLT, especially in patients with TMALS at day 14 and 28 after LDLT. High molecular weight multimers of VWF were observed to have increased in patients with LDLT, and the high molecular weight multimers of VWF were further increased in those with mild TMALS but they decreased in those with severe TMA. These findings suggest that ULM- VWF and ADAMTS13 might be associated with the onset of TMA after LT. [Copyright &y& Elsevier]

Thrombotic thrombocytopenic purpura (TTP) is a fulminant disease characterized by platelet aggregates, thrombocytopenia, renal insufficiency, neurologic changes, and mechanical injury to erythrocytes. Most idiopathic cases of TTP are characterized by a deficiency of ADAMTS13 (a disintegrin and metalloprotease, with thrombospondin-1-like domains) metalloprotease activity. Ironically, use of anti-platelet agents, the thienopyridine derivates clopidogrel and ticlopidine, is associated with drug induced TTP. Data were abstracted from a systematic review of English-language literature for thienopyridine-associated TTP identified in MEDLINE, EMBASE, the public website of the Food and Drug Administration, and abstracts from national scientific conferences from 1991 to April 2008. Ticlopidine and clopidogrel are the two most common drugs associated with TTP in FDA safety databases. Epidemiological studies identify recent initiation of anti-platelet agents as the most common risk factor associated with risks of developing TTP. Laboratory studies indicate that most cases of thienopyridine-associated TTP involve an antibody to ADAMTS13 metalloprotease, present with severe thrombocytopenia, and respond to therapeutic plasma exchange (TPE); a minority of thienopyridine-associated TTP presents with severe renal insufficiency, involves direct endothelial cell damage, and is less responsive to TPE. The evaluation of this potentially fatal drug toxicity can serve as a template for future efforts to comprehensively characterize other severe adverse drug reactions.Kidney International (2009) 75, S20–S24; doi:10.1038/ki.2008.613 [ABSTRACT FROM AUTHOR]

Abstract: The ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type I domain 13) activity was measured by a fluorescence resonance energy transfer (FRET) assay in the plasma of healthy volunteers and thrombotic thrombocytopenic purpura (TTP) patients to examine its usefulness in the diagnosis of TTP. The plasma levels of the ADAMTS13 activity did not show a normal distribution. Its median value was 107% (range: 55–170%) in healthy volunteers, but was significantly lower in patients with TTP (acquired or familial) and in patients with hematopoietic stem cell transplantation. However, it was not significantly lower in patients with antiphospholipid syndrome (APS). The ADAMTS13 activity by a FRET assay was closely correlated with that by the ADAMTS13 multimer method (r =0.816; p <0.001). In 18 patients with less than 10% of ADAMTS13 activity by FRET assay, less than 10% of that by multimer assay was 16, thus suggesting a good correlation for a low level of ADAMTS13. These findings suggest that the ADAMTS13 FRET assay correlates well with the ADAMTS13 multimer method and it is therefore useful for making a diagnosis of TTP. [Copyright &y& Elsevier]

We encountered the case of a 4-year-old boy with thrombotic microangiopathy (TMA) of unknown etiology. Verotoxin-induced hemolytic uremic syndrome (HUS), Streptococcus-pneumoniae-related HUS, factor H deficiency, drug-induced thrombotic thrombocytopenic purpura (TTP), and ADAMTS13 (von Willebrand factor-cleaving protease; a disintegrin-like and metalloprotease with thrombospondin type 1 repeats)-related TTP were excluded. His condition was refractory to anticoagulants and plasma exchange, and his clinical course was catastrophic, with central nervous system symptoms and progressive renal failure. However, factual treatment of intravenous gamma globulin (IVIG) ended the hemolysis and resulted in a rise in platelet count. He fully recovered except for end-stage renal failure, but he underwent a successful renal transplant after peritoneal dialysis. He has not suffered a relapse of TMA or an allograft rejection for 4 years. IVIG might be an option for some patients with TMA of unknown etiology refractory to conventional treatment. [ABSTRACT FROM AUTHOR]

A 59-year-old woman, diagnosed with chronic myelogenous leukemia (chronic phase) and treated with interferon-α for 13 years, developed renal failure. Renal biopsy showed thrombotic thrombocytopenic purpura, but intensive therapy including plasma exchange and steroid administration was not effective. The activity of von Willebrand factor-cleaving protease was detectable at the intermediate level (15–46%) during the clinical course, suggesting that this case was not compatible with the previously reported pattern of idiopathic or drug-induced thrombotic thrombocytopenic purpura, but with the pattern associated with malignant disease or immunological disorders. Further studies to determine the effects of interferon-α on endothelial cells in chronic myelogenous leukemia patients are needed. Copyright © 2005 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

von Willebrand factor (VWF) is synthesized primarily in vascular endothelial cells and secreted into the plasma as unusually large VWF multimers. Normally, these multimers are quickly degraded into smaller forms by a plasma metalloproteinase, VWF-cleaving protease (VWF-CP). Decreases in the activity of this enzyme result in congenital and acquired thrombotic thrombocytopenic purpura (TTP). The human VWF-CP has recently been purified. Cloning of the corresponding cDNA revealed that the 1,427-aa polypeptide is a member of the ADAMTS gene family, termed ADAMTS13. Twelve rare mutations in this gene have been identified in patients with congenital TTP. Here, we report missense and nonsense mutations in two Japanese families with Upshaw-Schulman syndrome, congenital TTP with neonatal onset and frequent relapses. The comparison of individual ADAMTS13 genotypes and plasma VWF-CP activities indicated that the R268P, Q449stop, and C508Y mutations abrogated activity of the enzyme, whereas the P4756 mutant retained low but significant activity. The effects of these mutations were further confirmed by expression analysis in HeLa cells. Recombinant VWF-CP containing either the R268P or C508Y mutations was not secreted from cells. In contrast, Q449stop and P4756 mutants were normally secreted but demonstrated minimal activity. Genotype analysis of 364 Japanese subjects revealed that P4755 is heterozygous in 9.6% of individuals, suggesting that approximately 10% of the Japanese population possesses reduced VWF-CP activity. We report on a single-nucleotide polymorphism associated with alterations in VWF-CP activity; it will be important to assess this single-nucleotide polymorphism as a risk factor for thrombotic disorders. [ABSTRACT FROM AUTHOR]

Background: Severe deficiency of vWF-cleaving protease (vWF-CPase) activity was recently found in patients with thrombotic thrombocytopenic purpura (TTP). Although the survival of patients with TTP has been dramatically improved with plasma exchange (PE), there are still many patients who are refractory to PE and immunosuppressive therapy.Study Design and Methods: The activities of vWF-CPase and its inhibitor were measured in 27 patients with nonfamilial TTP and hemolytic-uremic syndrome (HUS) to examine the relationship between the clinical variables and vWF-CPase activity.Results: Eight of nine patients with HUS had more than 40 percent of vWF-CPase activity, whereas one had 28 percent of the normal level at the acute phase. Ten of 12 TTP patients with a good outcome had a severe deficiency of vWF-CPase activity and its inhibitor, whereas four of six patients with a poor outcome had a moderate deficiency of vWF-CPase activity along with a lack of the inhibitor. PE produced normalization of the vWF-CPase activity and neutralization of the inhibitor in TTP patients with a good outcome; however, some TTP patients with vWF-CPase inhibitor had relapsed and required an immunosuppressive therapy. The response to the combination therapy with PE and immunosuppressive treatment was poor in TTP patients without a severe deficiency of vWF-CPase activity.Conclusion: Assays of vWF-CPase activity and its inhibitor may be useful for predicting the response to therapy and the outcome of patients with TTP. In some patients, nonfamilial TTP with a poor prognosis may not be caused by a constitutional or acquired deficiency of vWF-CPase with its inhibitor. Although PE and immunosuppressive therapy are effective in patients with nonfamilial TTP and a vWF-CPase inhibitor, other therapeutic modalities may be needed for nonfamilial TTP with unknown etiology. [ABSTRACT FROM AUTHOR]

Upshaw- Schulman syndrome ( USS) involves a congenital deficiency of von Willebrand factor-cleaving metalloprotease ( ADAMTS13) activity due to gene mutations. Female patients develop overt thrombotic thrombocytopenic purpura ( TTP) caused by a decline of ADAMTS13 activity in pregnancy. A 23-year-old nulliparous Japanese woman died due to severe, rapid progression of TTP with intrauterine fetal death at 20 weeks of gestation after its onset, even though she underwent intensive treatment which included plasma exchange. She had a history of idiopathic thrombocytopenic purpura at the age of 3 years. The patient's ADAMTS13 activity was of very low level. It should be borne in mind that there is the possibility of rapidly progressive fulminant USS during pregnancy. [ABSTRACT FROM AUTHOR]

The article presents a case study of an 11-year-old girl diagnosed with pediatric idiopathic thrombotic thrombocytopenic purpura (TTP). The rare disease was caused by a decrease in the activity of thrombospondin type 1 motif, member 13 (ADAMTS13). Treatment of pediatric idiopathic TTP with plasma exchange is highlighted.

Thrombotic thrombocytopenic purpura (TTP) is a fulminant disease characterized by platelet aggregates, thrombocytopenia, renal insufficiency, neurologic changes, and mechanical injury to erythrocytes. Most idiopathic cases of TTP are characterized by a deficiency of ADAMTS13 ( a d isintegrin a nd m etalloprotease, with t hrombo s pondin-1-like domains) metalloprotease activity. Ironically, use of anti-platelet agents, the thienopyridine derivates clopidogrel and ticlopidine, is associated with drug induced TTP. Data were abstracted from a systematic review of English-language literature for thienopyridine-associated TTP identified in MEDLINE, EMBASE, the public website of the Food and Drug Administration, and abstracts from national scientific conferences from 1991 to April 2008. Ticlopidine and clopidogrel are the two most common drugs associated with TTP in FDA safety databases. Epidemiological studies identify recent initiation of anti-platelet agents as the most common risk factor associated with risks of developing TTP. Laboratory studies indicate that most cases of thienopyridine-associated TTP involve an antibody to ADAMTS13 metalloprotease, present with severe thrombocytopenia, and respond to therapeutic plasma exchange (TPE); a minority of thienopyridine-associated TTP presents with severe renal insufficiency, involves direct endothelial cell damage, and is less responsive to TPE. The evaluation of this potentially fatal drug toxicity can serve as a template for future efforts to comprehensively characterize other severe adverse drug reactions. [ABSTRACT FROM AUTHOR]