Successful management of refractory immune-mediated thrombotic thrombocytopenic purpura during pregnancy and delivery using the anti-VWF nanobody caplacizumab.

Pregnancy is a potential trigger of acute thrombotic thrombocytopenic purpura (TTP). The management of pregnancy-associated immune-mediated TTP (iTTP) can be challenging, especially when it is refractory to standard treatment. Caplacizumab, a nanobody to von Willebrand factor (VWF) blocking its A1 domain, is a valuable new therapeutic option. Its use is, however, not approved during pregnancy and breastfeeding. We describe the successful off-label administration of caplacizumab during pregnancy and delivery in a patient with refractory iTTP. The favourable outcome without significant thrombotic or haemorrhagic complications indicates that caplacizumab may be an effective and safe treatment option in refractory iTTP during pregnancy.

Severe high-molecular-weight kininogen deficiency: clinical characteristics, deficiency-causing KNG1 variants, and estimated prevalence.

BACKGROUND: Severe high-molecular-weight kininogen (HK) deficiency is a poorly studied autosomal recessive contact system defect caused by pathogenic, biallelic KNG1 variants. AIM: We performed the first comprehensive analysis of diagnostic, clinical, genetic, and epidemiological aspects of HK deficiency. METHODS: We collected clinical information and blood samples from a newly detected HK-deficient individual and from published cases identified by a systematic literature review. Activity and antigen levels of coagulation factors were determined. Genetic analyses of KNG1 and KLKB1 were performed by Sanger sequencing. The frequency of HK deficiency was estimated considering truncating KNG1 variants from GnomAD. RESULTS: We identified 48 cases of severe HK deficiency (41 families), of these 47 have been previously published (n = 19 from gray literature). We genotyped 3 cases and critically appraised 10 studies with genetic data. Ten HK deficiency-causing variants (one new) were identified. All of them were truncating mutations, whereas the only known HK amino acid substitution with a relevant phenotype instead causes hereditary angioedema. Conservative estimates suggest an overall prevalence of severe HK deficiency of approximately one case per 8 million population, slightly higher in Africans. Individuals with HK deficiency appeared asymptomatic and had decreased levels of prekallikrein and factor XI, which could lead to misdiagnosis. CONCLUSION: HK deficiency is a rare condition with only few known pathogenic variants. It has an apparently good prognosis but is prone to misdiagnosis. Our understanding of its clinical implications is still limited, and an international prekallikrein and HK deficiency registry is being established to fill this knowledge gap.

Maternal mortality related to pulmonary embolism in the United States, 2003-2020.

BACKGROUND: Pulmonary embolism is a leading cause of maternal morbidity and mortality in Western countries. In the United States, pulmonary embolism-related mortality rates have plateaued in the general population after an initial decrease in the past 20 years. OBJECTIVE: This study aimed to describe the changes in pulmonary embolism-related maternal mortality rates in the United States over the past 2 decades. STUDY DESIGN: In this epidemiologic study of public vital registration data (death certificates encompassing underlying and contributing causes of death) from the Centers for Disease Control and Prevention Multiple Cause of Death database (2003-2020), we identified all maternal deaths with a pulmonary embolism code listed in any position of the death certificates. We investigated the changes in annual crude pulmonary embolism-related maternal mortality rates for the years 2003 to 2020, considering the effect of the introduction of the pregnancy checkbox in death certificates on the pulmonary embolism-related maternal mortality rates. RESULTS: Overall, 735 pulmonary embolism-related maternal deaths out of 12,871 total maternal deaths (5.7%) were recorded between 2003 and 2020; the overall pulmonary embolism-related maternal mortality rate was 1.02 (95% confidence interval, 0.95-1.10) per 100,000 live births. The pulmonary embolism-related maternal mortality rate increased from 0.93 in 2003 to 1.96 in 2020; however, when accounting for the implementation of the pregnancy checkbox in the death certificates, the trends in pulmonary embolism-related maternal mortality were largely unchanged from 2003 to 2020. The crude pulmonary embolism-related maternal mortality rates differed across maternal age groups (overall 0.61, 1.09, and 3.83 maternal deaths per 100,000 live births for those aged ≤24, 25-39, and ≥40 years, respectively) and racial/ethnicity groups (2.89, 0.47, 0.77, and 0.63 maternal deaths per 100,000 live births for Black non-Hispanics, other non-Hispanics, White non-Hispanics, and Hispanics, respectively). CONCLUSION: Maternal mortality rates related to pulmonary embolism did not decrease during the period from 2003 to 2020, as opposed to mortality rates related to pulmonary embolism in the general population. More research is required to assess whether improvement in venous thromboembolism prevention and pulmonary embolism diagnosis and management strategies might reduce death owing to pulmonary embolism in this vulnerable population.

EHA Guidelines on Management of Antithrombotic Treatments in Thrombocytopenic Patients With Cancer.

In cancer patients, thrombocytopenia can result from bone marrow infiltration or from anticancer medications and represents an important limitation for the use of antithrombotic treatments, including anticoagulant, antiplatelet, and fibrinolytic agents. These drugs are often required for prevention or treatment of cancer-associated thrombosis or for cardioembolic prevention in atrial fibrillation in an increasingly older cancer population. Data indicate that cancer remains an independent risk factor for thrombosis even in case of thrombocytopenia, since mild-to-moderate thrombocytopenia does not protect against arterial or venous thrombosis. In addition, cancer patients are at increased risk of antithrombotic drug-associated bleeding, further complicated by thrombocytopenia and acquired hemostatic defects. Furthermore, some anticancer treatments are associated with increased thrombotic risk and may generate interactions affecting the effectiveness or safety of antithrombotic drugs. In this complex scenario, the European Hematology Association in collaboration with the European Society of Cardiology has produced this scientific document to provide a clinical practice guideline to help clinicians in the management of patients with cancer and thrombocytopenia. The Guidelines focus on adult patients with active cancer and a clear indication for anticoagulation, single or dual antiplatelet therapy, their combination, or reperfusion therapy, who have concurrent thrombocytopenia because of either malignancy or anticancer medications. The level of evidence and the strength of the recommendations were discussed according to a Delphi procedure and graded according to the Oxford Centre for Evidence-Based Medicine.

c.451dupT in KLKB1 is common in Nigerians, confirming a higher prevalence of severe prekallikrein deficiency in Africans compared to Europeans.

Essentials Prekallikrein (PK) deficiency is a recessive trait with isolated aPTT prolongation. KLKB1 c.451dupT is common in Nigerians (7/600 alleles) and absent in a European group (0/600). To date, all genotyped PK-deficient patients of African ancestry were homozygous for 451dupT. Diagnostics of isolated aPTT prolongation in African descendants should include PK testing. ABSTRACT: Background Severe prekallikrein deficiency (PK deficiency) is an autosomal-recessive condition thought to be very rare. Recently we reported that the previously unnoticed variant c.451dupT, p.Ser151Phefs*34 in KLKB1, which is listed in databases aggregating genome data, causes PK deficiency and is common in Africans according to gnomAD (allele frequency 1.43%). Patients/Methods The most common African (c.451dupT) and European (c.1643G>A, p.Cys548Tyr) PK deficiency causing KLKB1 variants were analyzed in two population-based collectives of 300 Nigerian and 300 German subjects. Genome databases were evaluated for variant frequencies and ethnicity of the subjects. The geographic origin of PK-deficient cases due to 451dupT was assessed. Results Two of five patients with PK deficiency caused by homozygous 451dupT were African, one African American, one from Oman, and one of unknown origin. The frequency of 451dupT was 1.17% in the Nigerian collective (7/600 alleles); none had Cys548Tyr. Subjects with 451dupT were found among different Nigerian ethnicities. Both variants were absent in the European collective. Database research was compatible with these findings, even though mainly data of African Americans (451dupT: 1.12%-1.78%) was accessible. A relevant number of non-American Africans are included only in the 1000Genomes collective: 451dupT frequency was 1.29% in native Africans and 1.56% in African Caribbeans. Conclusions This study underlines the higher prevalence of PK deficiency among people with African descent compared to Europeans. In order to avoid delay of necessary surgical procedures in patients of African origin, diagnostic algorithms for isolated, unexplained, activated partial thromboplastin time prolongation in these subjects should include PK deficiency screening.

The Evolution of Hemophilia Care: Clinical and Laboratory Advances, Opportunities, and Challenges.

Hemophilia A (HA) and B (HB) are X-linked bleeding disorders caused by mutations in the F8 or F9 gene that result in the absence, or reduced activity, of the corresponding clotting factor. The severity of bleeding and related complications is proportional to the amount of residual circulating functional factor. The development of a safe and effective hemophilia treatment lasted several decades and has been mainly based on clotting factor replacement. Advances in the engineering and manufacturing of clotting concentrates have led to the widespread availability of extended half-life products that reduced the number of intravenous infusions needed to achieve adequate trough levels. The recent development of new nonfactor replacement treatments and biotechnology techniques has offered therapeutic alternatives for hemophilia patients with and without inhibitors. These are characterized by an easier route of administration, low immunogenicity, and, regarding gene therapy and cell-based treatments, potential long-term protection from bleeding after a single treatment course. In this review, we analyze recent progresses in the management of hemophilia and discuss opportunities and challenges.

Severe plasma prekallikrein deficiency: Clinical characteristics, novel KLKB1 mutations, and estimated prevalence.

BACKGROUND: Severe plasma prekallikrein (PK) deficiency is an autosomal-recessive defect characterized by isolated activated partial thromboplastin time prolongation. To date, no comprehensive methodologically firm analysis has investigated the diagnostic, clinical, and genetic characteristics of PK deficiency, and its prevalence remains unknown. PATIENTS/METHODS: We described new families with PK deficiency, retrieved clinical and laboratory information of cases systematically searched in the (gray) literature, and collected blood of these cases for complementary analyses. The Genome Aggregation Database (gnomAD) and the population-based Gutenberg Health Study served to study the prevalence of mutations and relevant genetic variants. RESULTS: We assembled a cohort of 111 cases from 89 families and performed new genetic analyses in eight families (three unpublished). We identified new KLKB1 mutations, excluded the pathogenicity of some of the previously described ones, and estimated a prevalence of severe PK deficiency of 1/155 668 overall and 1/4725 among Africans. One individual reported with PK deficiency had, in fact, congenital kininogen deficiency associated with decreased PK activity. One quarter of individuals had factor XII clotting activity below the reference range. Four major bleeding events were described in 96 individuals, of which 3 were provoked, for a prevalence of 4% and an annualized rate of 0.1%. The prevalence of cardiovascular events was 15% (6% <40 years; 21% 40-65 years; 33% >65 years) for an annualized rate of 0.4%. CONCLUSIONS: We characterized the genetic background of severe PK deficiency, critically appraised mutations, and provided prevalence estimates. Our data on laboratory characteristics and clinical course of severe PK deficiency may have clinical implications.

Recurrence Risk after First Symptomatic Distal versus Proximal Deep Vein Thrombosis According to Baseline Risk Factors.

Background It remains unclear whether the distal location of deep vein thrombosis (DVT) is independently associated with a lower risk of recurrence in all patients, or represents a marker of the presence and severity of provoking factors for venous thromboembolism (VTE). Methods We investigated the impact of distal (vs. proximal) DVT location on the risk of developing symptomatic, objectively confirmed recurrent VTE in 831 patients with a first acute symptomatic DVT not associated with pulmonary embolism (PE), who were stratified by the presence of transient or persistent risk factors at baseline. The primary outcome was symptomatic, objectively diagnosed recurrent VTE, including proximal DVT and PE. Results A total of 205 (24.7%) patients presented with a transient risk factor, 189 (22.7%) with a minor persistent risk factor, 202 (24.3%) with unprovoked DVT, and 235 (28.3%) with cancer-associated DVT. One-hundred twenty-five patients (15.0%) experienced recurrent DVT or PE. The largest relative difference between patients with distal (vs. proximal) DVT was observed in the absence of identifiable risk factors (adjusted hazard ratio [aHR]: 0.11; 95% CI [confidence interval]: 0.03-0.45). In patients with cancer, distal and proximal DVT had a comparable risk of recurrence (aHR: 0.70; 95% CI: 0.28-1.78]). Conclusions The distal (vs. proximal) location of first acute symptomatic DVT represented, in the absence of any identifiable transient or persistent risk factors, a favorable prognostic factor for recurrence. In contrast, the prognostic impact of DVT location was weaker if persistent provoking risk factors for VTE were present, notably cancer.

Sex-specific differences in the distal versus proximal presenting location of acute deep vein thrombosis.

BACKGROUND AND AIMS: Women present with pulmonary embolism (PE) more often than men, while the opposite is true for proximal deep vein thrombosis (DVT). We investigated whether sex-specific differences exist in the presenting location of acute symptomatic DVT among patients without concomitant PE. METHODS: We tested our hypothesis in a meta-analysis of studies selected by systematically reviewing PubMed, Embase, and the grey literature. Thereafter, we analysed data of a single-center cohort including patients with first isolated acute DVT to assess the additional impact of age and provoking risk factors on the presenting location of DVT. RESULTS: We identified 7 studies for a total of 20,534 patients. The weighed pooled absolute difference in the proportion of distal DVT between women and men was +5.4% (95%CI: +0.7%; +9.5%), which corresponds to a pooled odds ratio (OR) of 1.30 (95%CI: 1.07-1.58). This difference was +6.5% (95%CI: +2.1%; +10.9%) for first distal DVT (OR 1.38; 95%CI: 1.11-1.72) and +5.3% (95%CI: +0.5%; +10.0%) for either first or recurrent distal DVT (OR 1.29; 95%CI: 1.03-1.61). In the cohort study, the larger difference in the proportion of distal DVT between women and men was observed among patients aged 51-70 (+9.5%; 95CI: +2.8%; +16.0% compared to those aged 18-50) or with unprovoked events (+8.5%; 95CI: -0.9%; +17.9%). CONCLUSIONS: Among patients with first symptomatic isolated acute DVT, women presented with distal DVT more often than men, whereas men had a higher proportion of proximal DVT events. This pattern appeared to depend on age and the absence of provoking risk factors for VTE.

Platelet haemostatic properties in ß-thalassaemia: the effect of blood transfusion.

BACKGROUND: Patients with thalassaemia may have thromboembolic events and, even without thrombosis, they have a subclinical hypercoagulable state. In this setting, several coagulation laboratory abnormalities have been described, but thus far no studies have explored the contribution of platelet adhesive and procoagulant properties to blood clotting activation. In this study, we dissected the platelet procoagulant effect and influence of blood transfusions on haemostasis and platelet function in thalassaemic patients. MATERIAL AND METHODS: Sixteen subjects with thalassaemia were studied (9 with transfusion-dependent ß-thalassaemia, 7 "trait" carriers). Splenectomised and non-splenectomised patients undergoing blood transfusion were compared. All splenectomised patients were then compared to "trait" carriers and to healthy controls (n=9). The following parameters were measured in transfusion-dependent patients before and after monthly transfusions and compared to those of controls: levels of platelet surface activation markers (P-selectin, tissue factor, and fibrinogen), whole blood platelet aggregation, tissue factor or adenosine diphosphate (ADP)-induced platelet thrombin generation (TG) potential, and D-dimer. RESULTS: Before transfusion, platelets from splenectomised patients showed significantly higher ADP-induced tissue factor expression, ADP- and collagen-induced platelet aggregation and TG potential than those from non-splenectomised patients and controls. Blood transfusion in splenectomised patients reduced platelet activation, aggregation and TG potential. DISCUSSION: Splenectomised patients with ß-thalassaemia had a prothrombotic state, characterised by enhanced platelet reactivity and function, and high platelet-induced TG potential. One hour after blood transfusions platelet and coagulation parameters improved, supporting the hypothesis that transfusion might have a protective role on platelet haemostatic status.