Donald S. Houston

Mutations in the mechanotransduction protein PIEZO1 are associated with hereditary xerocytosis

Hereditary xerocytosis (HX, MIM 194380) is an autosomal dominant hemolytic anemia characterized by primary erythrocyte dehydration. Copy number analyses, linkage studies, and exome sequencing were used to identify novel mutations affecting PIEZO1, encoded by the FAM38A gene, in 2 multigenerational HX kindreds. Segregation analyses confirmed transmission of the PIEZO1 mutations and cosegregation with the disease phenotype in all affected persons in both kindreds. All patients were heterozygous for FAM38A mutations, except for 3 patients predicted to be homozygous by clinical and physiologic studies who were also homozygous at the DNA level. The FAM38A mutations were both in residues highly conserved across species and within members of the Piezo family of proteins. PIEZO proteins are the recently identified pore-forming subunits of channels that mediate mechanotransduction in mammalian cells. FAM38A transcripts were identified in human erythroid cell mRNA, and discovery proteomics identified PIEZO1 peptides in human erythrocyte membranes. These findings, the first report of mutation in a mammalian mechanosensory transduction channel-associated with genetic disease, suggest that PIEZO proteins play an important role in maintaining erythrocyte volume homeostasis.

Anemia of chronic disease: A harmful disorder or an adaptive, beneficial response?

Anemia of chronic disease is a hypoproliferative anemia that develops in response to systemic illness or inflammation.[1][1] It was first described in the 1930s and was more fully characterized by Cartwright and Wintrobe in the 1950s.[2][2] Although the second most prevalent after anemia caused by

Early intravenous unfractionated heparin and mortality in septic shock

Background:Sepsis and septic shock represent a systemic inflammatory state with substantial pro-coagulant elements. Unfractionated heparin is a known anticoagulant, which also possesses anti-inflammatory properties. Unfractionated heparin has been shown to increase survival in experimental models of septic shock. Objective:To evaluate the impact of intravenous therapeutic dose unfractionated heparin in a cohort of patients diagnosed with septic shock. Design:Retrospective, propensity matched, multicenter, cohort study. Setting:Regional intensive care units in Winnipeg, Canada between 1989 and 2005. Patients:Two thousand three hundred fifty-six patients diagnosed with septic shock, of which 722 received intravenous therapeutic dose heparin. Measurements and Main Results:The primary outcome of study was 28-day mortality, and mortality stratified by severity of illness (Acute Physiologic and Chronic Health Evaluation II quartile). Safety was assessed by comparing rates of gastrointestinal hemorrhage, intracranial hemorrhage, and the need for transfusion. By using a Cox proportional hazards model, systemic heparin therapy was associated with decreased 28-day mortality (307 of 695 [44.2%] vs. 279 of 695 [40.1%]; hazard ratio 0.85 [confidence interval (CI) 95% 0.73–1.00]; p = 0.05). In the highest quartile of severity of illness (Acute Physiologic and Chronic Health Evaluation II score 29–53), heparin administration was associated with a clinically and statistically significant reduction in 28-day mortality [127 of 184 (69.0%) vs. 94 of 168 (56.0%); hazard ratio 0.70 (CI 95% 0.54–0.92); p = 0.01]. The use of intravenous unfractionated heparin was associated with successful liberation from mechanical ventilation [odds ratio of 1.42 (CI 95% 1.13–1.80); p = 0.003], and successful discontinuation of vasopressor/inotropic support [odds ratio of 1.34 (CI 95% 1.06–1.71); p = 0.01]. No significant differences in the rates of major hemorrhage or need for transfusion were identified. Conclusion:Early administration of intravenous therapeutic dose unfractionated heparin may be associated with decreased mortality when administered to patients diagnosed with septic shock, especially in patients with higher severity of illness. Prospective randomized trials are needed to further define the role of this agent in sepsis and septic shock.

The efficacy and safety of heparin in patients with sepsis: a systematic review and metaanalysis.

Objective:To evaluate the efficacy and safety of heparin in patients with sepsis, septic shock, or disseminated intravascular coagulation associated with infection. Design:Systematic review and metaanalysis. Data Sources:Randomized controlled trials from MEDLINE, EMBASE, CENTRAL, Global Health, Scopus, Web of Science, the International Clinical Trials Registry Platform (inception to April 2014), conference proceedings, and reference lists of relevant articles. Study Selection and Data Extraction:Two reviewers independently identified and extracted trial-level data from randomized trials investigating unfractionated or low molecular heparin administered to patients with sepsis, severe sepsis, septic shock, or disseminated intravascular coagulation associated with infection. Internal validity was assessed in duplicate using the Risk of Bias tool. The strength of evidence was assessed in duplicate using Grading of Recommendations Assessment, Development, and Evaluation methodology. Our primary outcome was mortality. Safety outcomes included hemorrhage, transfusion, and thrombocytopenia. Measurements and Main Results:We included nine trials enrolling 2,637 patients. Eight trials were of unclear risk of bias and one was classified as having low risk of bias. In trials comparing heparin to placebo or usual care, the risk ratio for death associated with heparin was 0.88 (95% CI, 0.77–1.00; I2 = 0%; 2,477 patients; six trials; moderate strength of evidence). In trials comparing heparin to other anticoagulants, the risk ratio for death was 1.30 (95% CI, 0.78–2.18; I2 = 0%; 160 patients; three trials; low strength of evidence). In trials comparing heparin to placebo or usual care, major hemorrhage was not statistically significantly increased (risk ratio, 0.79; 95% CI, 0.53–1.17; I2 = 0%; 2,392 patients; three trials). In one small trial of heparin compared with other anticoagulants, the risk of major hemorrhage was significantly increased (2.14; 95% CI, 1.07–4.30; 48 patients). Important secondary and safety outcomes, including minor bleeding, were sparsely reported. Conclusions:Heparin in patients with sepsis, septic shock, and disseminated intravascular coagulation associated with infection may be associated with decreased mortality; however, the overall impact remains uncertain. Safety outcomes have been underreported and require further study. Increased major bleeding with heparin administration cannot be excluded. Large rigorous randomized trials are needed to evaluate more carefully the efficacy and safety of heparin in patients with sepsis, severe sepsis, and septic shock.

Profiling Three-Dimensional Nuclear Telomeric Architecture of Myelodysplastic Syndromes and Acute Myeloid Leukemia Defines Patient Subgroups

Purpose: Myelodysplastic syndromes (MDS) are a group of disorders characterized by cytopenias, with a propensity for evolution into acute myeloid leukemias (AML). This transformation is driven by genomic instability, but mechanisms remain unknown. Telomere dysfunction might generate genomic instability leading to cytopenias and disease progression. Experimental Design: We undertook a pilot study of 94 patients with MDS (56 patients) and AML (38 patients). The MDS cohort consisted of refractory cytopenia with multilineage dysplasia (32 cases), refractory anemia (12 cases), refractory anemia with excess of blasts (RAEB)1 (8 cases), RAEB2 (1 case), refractory anemia with ring sideroblasts (2 cases), and MDS with isolated del(5q) (1 case). The AML cohort was composed of AML-M4 (12 cases), AML-M2 (10 cases), AML-M5 (5 cases), AML-M0 (5 cases), AML-M1 (2 cases), AML-M4eo (1 case), and AML with multidysplasia-related changes (1 case). Three-dimensional quantitative FISH of telomeres was carried out on nuclei from bone marrow samples and analyzed using TeloView. Results: We defined three-dimensional nuclear telomeric profiles on the basis of telomere numbers, telomeric aggregates, telomere signal intensities, nuclear volumes, and nuclear telomere distribution. Using these parameters, we blindly subdivided the MDS patients into nine subgroups and the AML patients into six subgroups. Each of the parameters showed significant differences between MDS and AML. Combining all parameters revealed significant differences between all subgroups. Three-dimensional telomeric profiles are linked to the evolution of telomere dysfunction, defining a model of progression from MDS to AML. Conclusions: Our results show distinct three-dimensional telomeric profiles specific to patients with MDS and AML that help subgroup patients based on the severity of telomere dysfunction highlighted in the profiles. Clin Cancer Res; 18(12); 3293–304. ©2012 AACR.

Activated protein C and septic shock: a propensity-matched cohort study*.

Background:Septic shock is a highly inflammatory and procoagulant state associated with significant mortality. In a single randomized controlled trial, recombinant human activated protein C (drotrecogin alfa) reduced mortality in patients with severe sepsis at high risk of death. Further clinical trials, including a recently completed trial in patients with septic shock, failed to reproduce these results. Objective:To evaluate the effectiveness of recombinant human activated protein C on mortality in a cohort of patients with septic shock and to explore possible reasons for inconsistent results in previous studies. Design:Retrospective, 2:1 propensity-matched, multicenter cohort study. Setting:Twenty-nine academic and community intensive care units in three countries. Patients:Seven thousand three hundred ninety-two adult patients diagnosed with septic shock, of which 349 received recombinant human activated protein C within 48 hrs of intensive care unit admission between 1997 and 2007. Measurements and Main Results:Our primary outcomes were mortality over 30 days and mortality stratified by Acute Physiology and Chronic Health Evaluation II quartile. Using a propensity-matched Cox proportional hazard model, we observed a 6.1% absolute reduction in 30-day mortality associated with the use of recombinant human activated protein C (108/311 [34.7%] vs. 254/622 [40.8%], hazard ratio 0.72, 95% confidence interval 0.52–1.00, p = .05) and noted consistent reductions in mortality among Acute Physiology and Chronic Health Evaluation II quartiles. A time to event analysis showed that the time to appropriate antimicrobials after documented hypotension decreased for each year of study (p = .003), a finding that was congruent with a decrease in annual mortality over the study period (odds ratio 0.96 per year [95% confidence interval 0.93–0.99], p = .003). Conclusions:In this retrospective, propensity-matched, multicenter cohort study of patients with septic shock, early use of recombinant human activated protein C was associated with reduced mortality. Improvements in general quality of care such as speed of antimicrobial delivery leading to decreasing mortality of patients with septic shock may have contributed to the null results of the recently completed trial of recombinant human activated protein C in patients with septic shock.

Continuous infusion of porcine factor VIII in the management of patients with factor VIII inhibitors.

The effectiveness of continuous infusion porcine factor VIII (PFVIII) has been evaluated in the treatment of 7 consecutive patients with factor VIII(FVIII) inhibitors. Two patients had hemophilia A and five were nonhemophiliacs with acquired FVIII inhibitors. The median pretreatment anti‐porcine FVIII titre was 0.2 (range: 0–15.0) Bethesda units (BU), and the anti‐human FVIII titer was 12.0 BU (range: 2.4–50.0). All patients presented with major bleeding. Patients were given a bolus dose of PFVIII followed by continuous infusion. Six patients also received immunosuppressive therapy. Therapeutic FVIII levels (>0.5 U/ml) were achieved in 6 of 7 patients at a median time of 12.5 hr, and then maintained with continuous infusion PFVIII. Six patients were treated for more than 7 days, and in four of these there was a decline in FVIII recovery between days 7 to 11, presumably related to a rising antibody response to PFVIII. These four patients were plasmapheresed and the three patients with autoantibodies recovered therapeutic FVIII levels but this did not occur in the patient with hemophilia. Thrombocytopenia developed in 4 patients at days 18 to 24, with the platelet count falling to 11 to 87 × 109/L, and the PFVIII was discontinued in 3 patients. All patients recovered from the acute bleeding events. With prolonged immunosuppressive therapy, the FVIII inhibitor disappeared in all patients with autoantibodies and there have been no relapses after a median follow‐up period of 581 days. This study demonstrates that continuous infusion PFVIII is an effective therapy for patients with FVIII inhibitors, but that prolonged treatment is associated with the development of inhibitors to porcine FVIII and severe thrombocytopenia, which readily corrects with discontinuation of PFVIII. Am. J. Hematol. 56:112–118, 1997.

Refinement of the hereditary xerocytosis locus on chromosome 16q in a large Canadian kindred

The hereditary stomatocytoses are a group of heterogeneous conditions associated with chronic red cell hemolysis for which the causative genetic mutations are not known. We investigated 137 members of a large Canadian kindred with phenotypic findings consistent with hereditary xerocytosis, one of the most common stomatocytosis syndromes. The objectives of this study were to characterize the clinical hallmarks of the hemolytic process, and to define the chromosomal region carrying the disease locus. The mode of inheritance was autosomal dominant. Affected family members had a well-compensated hemolysis, associated with an elevated MCHC, decreased osmotic fragility, decreased haptoglobin, and indirect hyperbilirubinemia. Cholelithiasis and progressive iron loading were common, despite normal hemoglobin levels. Quantitative erythrocyte morphologic evaluation revealed increased schistocytes, target cells, reticulocytes, and eccentrocytes in affected individuals; stomatocytes were not increased. Genetic linkage analysis confirmed the localization of the disease phenotype to chromosome 16q, and refined the candidate region to 16q24.2-16qter, a 2.4 million base pair interval containing 51 known or predicted genes.

Plasma homocysteine concentration is not associated with activated protein C resistance in patients investigated for hypercoagulability

Homocysteine and activated protein C (aPC) resistance are known risk factors for thromboembolism, but how elevated homocysteine influences thrombogenicity is not fully understood. The possibility that homocysteine may exert a pro-thrombotic effect by inducing aPC resistance has been addressed, with conflicting conclusions. The aim of this study is to evaluate the possible relationship of serum homocysteine concentration to aPC resistance in a cohort of patients investigated for hypercoagulability. Laboratory records from 1011 consecutive patients referred to the Haemostasis Laboratory at the Health Sciences Centre (Winnipeg, Canada) were reviewed from February 1997 to November 2002. Homocysteine levels, normalized aPC sensitivity ratio (aPC-SR), and Factor V Leiden genotype were recorded for all 1011 patients. 394 patients had aPC-SR determined by mixing the patient plasma in 4 parts FV deficient plasma (FV-deficient-mix assay), and 617 patients had aPC-SR calculated without mixing (neat assay). Homocysteine did not significantly influence the aPC-SR when using the FV deficient assay. When aPC-SR was measured using the neat assay, homocysteine was found to correlate inversely with the degree of aPC resistance. The mean aPC-SR of FV Leiden-negative subjects measured using the neat assay was substantially lower than the expected normalized value of 1.0 that was obtained when aPC-SR was measured with the FV-deficient-mix assay. aPC resistance is common in patients being evaluated for possible hypercoagulability. In these patients, elevated plasma homocysteine levels is not associated with aPC resistance regardless of FV Leiden genotype suggesting that this is not the mechanism by which homocysteine exerts a prothrombotic effect.

Preoperative therapeutic apheresis for severe medically refractory amiodarone-induced thyrotoxicosis: A case report

Introduction: Amiodarone is associated with thyroid dysfunction and life‐threatening thyrotoxicosis. In medically refractory cases, or where medical therapy is contraindicated, thyroidectomy may be required. To decrease perioperative thyroid storm and to reduce overall surgical risk, apheresis may be considered preoperatively to restore euthyroidism. Case Description: We report a 46‐year‐old female with a history of cardiac arrhythmia and tachycardia‐induced cardiomyopathy for which she received amiodarone. Months after discontinuation of amiodarone, the patient presented with wide complex tachycardia and symptoms of thyrotoxicosis. Laboratory testing confirmed severe thyrotoxicosis which was subsequently refractory to medical therapy. Total thyroidectomy was required. Following a total of 10 apheresis treatments, thyroid hormone levels were reduced to near normal levels and the patients symptoms improved. Thyroidectomy was performed without intraoperative or postoperative complication. Discussion: In the setting of life‐threatening, medically refractory amiodarone‐induced thyrotoxicosis, therapeutic apheresis can effectively reduce thyroid hormone levels and restore a state of clinical and biochemical euthyroidism. J. Clin. Apheresis 29:168–170, 2014.