Association between ADAMTS13 deficiency and cardiovascular events in chronic hemodialysis patients

A mild decrease of ADAMTS13 (a disintegrin and metalloprotease with thrombospodin type 1 motif 13) could attribute to stroke and coronary heart disease in general population. However, the role of ADAMTS13 in hemodialysis (HD) patients remains to be explored. This cross-sectional and observational cohort study enrolled 98 chronic HD patients and 100 normal subjects with the aims to compare the ADAMTS13 activity between chronic HD patients and normal subjects, and to discover the role of ADAMTS13 on the newly developed cardiovascular events for HD patients in a 2-year follow-up. Our HD patients had a significantly lower ADAMTS13 activity than normal subjects, 41.0 ± 22.8% versus 102.3 ± 17.7%, p < 0.001. ADAMTS13 activity was positively correlated with diabetes, triglyceride and hemoglobin A1c, and negatively with high-density lipoprotein cholesterol levels in HD patients. With a follow-up of 20.3 ± 7.3 months, the Cox proportional hazards model revealed that low ADAMTS13, comorbid diabetes, and coronary heart diseases have independent correlations with the development of cardiovascular events. Our study demonstrated that chronic HD patients have a markedly decreased ADAMTS13 activity than normal subjects. Although ADAMTS13 seems to correlate well with diabetes, high triglyceride and low high-density lipoprotein cholesterol levels, ADAMTS13 deficiency still carries an independent risk for cardiovascular events in chronic HD patients.

Microlyse; a thrombolytic agent that targets VWF for clearance of microvascular thrombosis

Thrombotic microangiopathies are hallmarked by attacks of disseminated microvascular thrombosis. In thrombotic thrombocytopenic purpura (TTP), this is caused by a rise in thrombogenic ultra-large von Willebrand factor (VWF) multimers because of ADAMTS13 deficiency. We previously reported that systemic plasminogen activation is therapeutic in a TTP mouse model. In contrast to its natural activators (i.e. tPA and uPA), plasminogen can directly bind to VWF. For optimal efficacy and safety, we aimed to focus and accelerate plasminogen activation at sites of microvascular occlusion. We here describe the development and characterization of Microlyse, a fusion protein consisting of a high-affinity VHH targeting the CT/CK domain of VWF and the protease domain of uPA, for localized plasminogen activation on microthrombi. Microlyse triggers targeted destruction of platelet-VWF complexes by plasmin on activated endothelial cells and in agglutination studies. At equal molar concentrations, Microlyse degrades microthrombi 7-fold more rapidly than blockade of platelet-VWF interactions with a bivalent humanized VHH (caplacizumab*). Finally, Microlyse attenuates thrombocytopenia and tissue damage (reflected by increased plasma lactate dehydrogenase activity, as well as PAI-1 and fibrinogen levels) more efficiently than caplacizumab* in an ADAMTS13-/- mouse model of TTP, without affecting hemostasis in a tail-clip bleeding model. These findings show that targeted thrombolysis of VWF by Microlyse is an effective strategy for the treatment of TTP and might hold value for other forms of VWF-driven thrombotic disease.

Daratumumab for immune thrombotic thrombocytopenic purpura

Immune thrombotic thrombocytopenic purpura (iTTP) is a life-threatening thrombotic microangiopathy. It is caused by a severe ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 motifs, 13) deficiency due to circulating autoantibodies, and is associated with significant morbidity and mortality. Current treatment options include plasma exchange, immunosuppression, and caplacizumab. When remission is achieved, the risk of relapse is high, especially in patients with persistent ADAMTS13 deficiency. We report the eradication of persistent ADAMTS13 inhibitory autoantibodies and restoration of normal ADAMTS13 activity using the anti-CD38 antibody daratumumab in two patients with iTTP. One patient had a frequently relapsing course, and the other a treatment-refractory first episode. There were no relevant adverse drug reactions.

Cancer Associated Microangiopathic Hemolytic Anemia: A Rare Paraneoplastic Syndrome

Microangiopathic hemolytic anemias (MAHA) are secondary to damage of RBCs because of endothelial vascular damage of blood vessels leading to hemolysis. MAHAs are characterized by negative coombs test and are associated with several etiologies that include can be either hereditary complement or ADAMTS13 deficiency or sepsis or malignancy. Cancer associated MAHA (CA-MAHA) is a rare and is seen in patients with advanced metastatic disease. CA-MAHA has significant mortality rate and chemotherapy is the only therapeutic option, however overall survival is poor. Here we, present a rare case of CA-MAHA secondary to metastatic signet ring cell carcinoma with an unknown primary. In patients, when the cause of progressive MAHA is unknown, the possibility of cancer associated MAHA must be considered and a comprehensive work up for an underlying malignancy must be done.

Annual Incidence and Severity of Acute Episodes in Hereditary Thrombotic Thrombocytopenic Purpura

Hereditary thrombotic thrombocytopenic purpura (hTTP) is a rare thrombotic microangiopathy characterized by severe congenital ADAMTS13 deficiency and recurring acute episodes causing morbidity and premature death. Information on the annual incidence and severity of acute episodes in hTTP patients is largely lacking. This study reports prospective data of 87 patients from the Hereditary TTP Registry (ClinicalTrials.gov NCT01257269) for survival, frequency and severity of acute episodes from enrollment until December 2019. The 87 patients, followed for median 4.2 years (range 0.01-15), had a median age at overt disease onset and at clinical diagnosis of 4.6 years and of 18 years (range 0.0-70 for both), respectively. Forty-three patients received regular plasma prophylaxis, while 22 did not, and treatment changed over time or was unknown in the remaining 22. Forty-three patients experienced 131 acute episodes of which 91 (69%) occurred in patients on regular prophylaxis. This resulted in an annual incidence of acute episodes of 0.36 (95%CI 0.29-0.44) with and of 0.41 (95%CI 0.30-0.56) without regular plasma treatment. More than one third of acute episodes (n=51) were documented in children &lt;10 years of age at enrollment and were often triggered by infections. Their annual incidence of acute episodes was significantly higher than in patients &gt;40 years of age (1.18 [95% CI 0.88-1.55] vs. 0.14 [95% CI 0.08-0.23]). Prophylactic plasma infusion regimens used were insufficient to prevent acute episodes in many patients. Such regimens are burdensome, caregivers, patients and their guardians are reluctant to start regular plasma infusions, from which particularly children would benefit.

Stroke and splenic infarct in a 17-year-old patient with COVID-associated hypercoagulable state and relative ADAMTS13 deficiency

In this case report, we present the case of a 17-year-old stroke patient suffering from coronavirus disease (COVID)-19. He was successfully treated with intravenous and endovascular treatment. After extensive work-up, a hypercoagulable state due to the COVID-19 infection was assumed as probable cause of stroke.

Comparative Analysis of Clinical Prediction Scores in Acquired Thrombotic Thrombocytopenic Purpura: The Superiority of Plasmic Score

Background: Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare and life-threatening hematologic disorder. The decision to start plasma exchange is challenging in clinical practice, due to aTTP rarity, and the extensive differential diagnosis with other thrombotic microangiopathies (TMA). Although the ADAMTS13 activity measurement is essential to aTTP diagnosis, a rapid quantification is unavailable in most centers, being necessary to develop clinical prediction models to evaluate severe enzymatic deficiency. The first model developed was Bentley score, followed by French score and more recently PLASMIC score. Studies comparing these 3 methods are scarce. The criteria of published scoring models are summarized in Table1 Aim: To compare and evaluate the discriminative power of the Bentley, French and PLASMIC scores in predicting severe ADAMTS13 deficiency (≤10%) in our group of patients (pts). Methods: We performed a retrospective analysis of pts with ADAMTS13 activity tested between 2008 and 2019, in a single center. Pts were divided in two groups: ADAMTS13 activity ≤10% (ADAMTS13≤10%) and &gt;10% (ADAMTS13&gt;10%) and then stratified according to the 3 scores. We evaluate sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) to predict low ADAMTS13 activity. Diagnostic accuracy was tested using the area under the ROC curve. A P-value of &lt;0.05 was considered statistically significant. Results: ADAMTS13 activity was evaluated in 119 pts with suspected aTTP. There was a female predominance (60.5%; n=72) and the mean age was 54±20 years. Thirty-one pts had ADAMTS13≤10% and 27 (87.1%) of them had been diagnosed with aTTP, two were inherited thrombotic thrombocytopenic purpura and the other two were sepsis associated TMA. Comparing the groups ADAMTS13≤10% and ADAMTS13&gt;10%, pts in the first were younger (46±18 vs 57±21 years; p=0.008), had lower platelet count (23.04±27.1 vs 47.79±37.6x109/L; p&lt;0.001), and lower creatinine value (1.25±0.8 vs 2.92±4.2 mg/dL; p&lt;0.017). ADAMTS13≤10% group had a higher reticulocyte count (5.99±5.0 vs 3.46±3.4%; p=0.005) and higher indirect bilirubin levels (2.59±2.1 vs 1.59±2.2 mg/dL; p=0.013). There were no statistical differences in hemoglobin, MCV, INR, D-Dimers and antinuclear antibodies (ANA's) positivity among the two groups. PLASMIC score was calculated in all pts. Due to missing data, Bentley score was only applied in 44.5% (n=53) and French score in 54.6% (n= 65) pts. Using a high-risk PLASMIC score as the predictor, the sensitivity was 80.6%, specificity 78.4%, PPV 56.8% and NPV 92.0%. The C-statistics for high PLASMIC score cut-offs (&gt;5 points) was 0.80 (95% confidence interval [CI] 0.70-0.89) (fig.1). Applying high-risk Bentley score vs low-to-intermediate-risk score, the sensitivity was 44.4%, specificity 94.3%, PPV 80.0% and NPV 76.7%. The C-statistics was 0.69 (95% CI 0.53-0.86) using the high Bentley score cut-offs (fig.2). The French score had higher sensitivity (83.3%), but lower specificity (36.2%), with 33.3% of PPV and 85.0% of NPV. Using the high French score cut-offs, the C-statistics was 0.60 (95% CI 0.45-0.75) (fig.3). There were not statistically significant differences between PLASMIC and Bentley scores in the ability to predict low ADAMTS13 activity, and both performed better than French score (p&lt;0.001; p=0.02, respectively). Conclusion: In our cohort, the PLASMIC score showed to be the most balanced and efficient clinical prediction score, with high sensitivity and specificity. Bentley score was also a good predictor of ADAMTS13 activity, but had lower sensitivity and less applicability; French score was comparatively inferior. Pts with low PLASMIC score are highly unlikely to have ADAMTS13 deficiency. PLASMIC score is easy to calculate and readily usable in most emergency settings while the French and Bentley scores require additional laboratory data, which is not always accessible. These results support the previously published data, showing PLASMIC score as a helpful complementary tool in clinical practice recognizing high-risk pts when ADAMTS13 activity measurement is not available. Disclosures No relevant conflicts of interest to declare.

Thrombotic thrombocytopenic purpura developed during the conservative treatment of anti-phospholipase A2 receptor antibody-positive idiopathic membranous nephropathy: a case report

Background Idiopathic membranous nephropathy (MN) is one of the major glomerulonephritis that cause nephrotic syndrome. The phospholipase A2 receptor (PLA2R) has recently been identified as an endogenous antigen of idiopathic MN. Thrombotic thrombocytopenic purpura (TTP) is a disorder characterized by schistocytes, hemolytic anemia, thrombocytopenia, and organ dysfunction which occurs as a result of thrombi. Patients with acquired TTP have autoantibodies against a disintegrin and metalloprotease with thrombospondin type 1 motif 13 (ADAMTS13). These autoantibodies act as an inhibitor and cause ADAMTS13 deficiency. Idiopathic MN and acquired TTP are usually considered as independent autoimmune diseases. We experienced a patient who developed TTP during the conservative treatment of idiopathic MN, with the coexistence of ADAMTS13 inhibitor and anti-PLA2R antibody. Case presentation A 73-year-old man presented with thrombocytopenia, hemolytic anemia, disturbance of consciousness, and acute kidney injury after 4-year course of biopsy-proven idiopathic MN. ADAMTS13 activity was undetectable and the ADAMTS13 inhibitor was identified. Additionally, he was positive for anti-PLA2R antibody. The patient did not have any diseases that could cause secondary thrombotic microangiopathy, and he was diagnosed with acquired TTP. Steroid therapy and plasma exchange were initiated and the acquired TTP resolved. MN achieved remission 3 months after the anti-PLA2R antibody disappeared. Conclusions This is the first reported case of acquired TTP developed during conservative treatment of idiopathic MN, with both ADAMTS13 inhibitor and anti-PLA2R antibody positive at the onset of the TTP. The present case suggests that idiopathic MN might be associated with the development of some cases of acquired TTP.