Early hydroxyurea use is neuroprotective in children with sickle cell anemia.

Children with sickle cell disease (SCD) who began hydroyxurea before age five years scored no differently on a measure of cognitive funciton than age, sex, and race-matched unaffected peers.

Early initiation of hydroxyurea (hydroxycarbamide) using individualised, pharmacokinetics-guided dosing can produce sustained and nearly pancellular expression of fetal haemoglobin in children with sickle cell anaemia.

Hydroxyurea (hydroxycarbamide) is an effective treatment for sickle cell anaemia (SCA), but clinical responses depend primarily upon the degree of fetal haemoglobin (HbF) induction and the heterogeneity of HbF expression across erythrocytes. The number and characteristics of HbF-containing cells (F-cells) are not assessed by traditional HbF measurements. Conventional hydroxyurea dosing (e.g. fixed doses or low starting doses with stepwise escalation) produces a moderate heterocellular HbF induction, but haemolysis and clinical complications continue. Robust, pancellular HbF induction is needed to minimise or fully inhibit polymerisation of sickle haemoglobin. We treated children with hydroxyurea using an individualised, pharmacokinetics-guided regimen starting at predicted maximum tolerated dose (MTD). We observed sustained HbF induction (mean >30%) for up to 6 years, which was not dependent on genetic determinants of HbF expression. Nearly 70% of patients had ≥80% F-cells (near-pancellular), and almost half had ≥90% F-cells (pancellular). The mean HbF/F-cell content was ~12 pg. Earlier age of initiation and better medication adherence were associated with high F-cell responses. In summary, early initiation of hydroxyurea using pharmacokinetics-guided starting doses at predicted MTD can achieve sustained near-pancellular or pancellular HbF expression and should be considered an achievable goal for children with SCA treated with hydroxyurea at optimal doses. Clinical trial registration number: NCT02286154 (clinicaltrials.gov).

Congenital dyserythropoietic anemia type I: First report from the Congenital Dyserythropoietic Anemia Registry of North America (CDAR).

Congenital dyserythropoietic anemias (CDAs) are characterized by ineffective erythropoiesis and distinctive erythroblast abnormalities; the diagnosis is often missed or delayed due to significant phenotypic heterogeneity. We established the CDA Registry of North America (CDAR) to study the natural history of CDA and create a biorepository to investigate the pathobiology of this heterogeneous disease. Seven of 47 patients enrolled so far in CDAR have CDA-I due to biallelic CDAN1 mutations. They all presented with perinatal anemia and required transfusions during infancy. Anemia spontaneously improved during infancy in three patients; two became transfusion-independent rapidly after starting interferon-α2; and two remain transfusion-dependent at last follow-up at ages 5 and 30 y.o. One of the transfusion-dependent patients underwent splenectomy at 11 y.o due to misdiagnosis and returned to medical attention at 27 y.o with severe hemolytic anemia and pulmonary hypertension. All patients developed iron overload even without transfusions; four were treated with chelation. Genetic testing allowed for more rapid and accurate diagnosis; the median age of confirmed diagnosis in our cohort was 3 y.o compared to 17.3 y.o historically. In conclusion, CDAR provides an organized research network for multidisciplinary clinical and research collaboration to conduct natural history and biologic studies in CDA.

Hydroyxurea improves cerebral oxygen saturation in children with sickle cell anemia.

Neurologic complications are common in patients with sickle cell anemia (SCA), but conventional tools such as MRI and transcranial Doppler ultrasonography (TCD) do not fully assess cerebrovascular pathology. Cerebral tissue oximetry measures mixed oxygen saturation in the frontal lobes (SCT O2 ) and provides early prognostic information about tissue at risk of ischemic injury. Untreated patients with SCA have significantly lower SCT O2 than healthy controls that declines with age. Hydroxyurea is effective in preventing many SCA-related complications, but the degree to which it preserves normal neurophysiology is unclear. We analyzed participants enrolled in the Therapeutic Response Evaluation and Adherence Trial (TREAT, NCT02286154), which enrolled participants initiating hydroxyurea using individualized dosing (new cohort) and those previously taking hydroxyurea (old cohort) and was designed to monitor the long-term benefits of hydroxyurea. Cerebral oximetry was performed at baseline and annually. For the new cohort (median starting age = 12 months, n = 55), mean baseline SCT O2 was normal before starting hydroxyurea (mean 65%, 95% CI 58-72%) and significantly increased after 2 years (mean 72%, 95% CI 65-79%, p < .001). The SCT O2 for patients receiving long-term hydroxyurea (median age = 9.6 years) was normal at study entry (mean 66%, 95% CI 58-74%) and remained stable across 2 years. Both cohorts had significantly higher SCT O2 than published data from predominantly untreated SCA patients. Cerebral oximetry is a non-invasive method to assess cerebrovascular pathology that complements conventional imaging. Our results indicate that hydroxyurea suggests protection against neurophysiologic changes seen in untreated SCA.

Implementation of near-universal hydroxyurea uptake among children with sickle cell anemia: A single-center experience.

BACKGROUND: Without early initiation of disease-modifying therapy, the acute and chronic complications of sickle cell anemia (SCA) begin early in childhood and progress throughout life. Hydroxyurea is a safe and effective medication that reduces or prevents most SCA-related complications. Despite recommendations to prescribe hydroxyurea for all children with SCA as young as 9 months, utilization remains low. PROCEDURE: We completed a retrospective review of hydroxyurea-prescribing practices and associated clinical outcomes at our institution over a 10-year period before and after the 2014 National Heart, Lung, and Blood Institute (NHLBI) recommendations to use hydroxyurea for all children with SCA. RESULTS: Hydroxyurea use more than doubled within our pediatric SCA population from 43% in 2010 to 95% in 2019. The age of hydroxyurea initiation was significantly younger during 2014-2019 compared to 2010-2013 (median 2 years vs. 6 years, p ≤ .001). With this change in clinical practice, nearly all (69/71 = 97%) children born after 2013 received disease-modifying therapy by the end of 2019, primarily hydroxyurea (93%). Concurrently, the number of SCA-related admissions significantly decreased from 67/100 patient-years in 2010 to 39/100 patient-years in 2019 (p < .001). CONCLUSION: The early and universal prescription of hydroxyurea for children with SCA is the standard of care. Here, we demonstrate that a careful and deliberate commitment to follow this guideline in clinical practice is feasible and results in measurable improvements in clinical outcomes. Our approach and improved outcomes can serve as a model for other programs to expand their hydroxyurea use for more children with SCA.

Non-transfusion-dependent ß-Thalassemia Because of a Single ß-Thalassemia Mutation and Coinherited α-Globin Gene Triplication: Need for Increased Awareness to Prevent Incorrect and Delayed Diagnosis.

The thalassemias are genetically complex and usually autosomal recessive. We describe 5 unrelated individuals with non-transfusion-dependent ß-thalassemia (NTDT), some with apparently dominant transmission, because of a single ß-thalassemia mutation coinherited with a triplicated α-globin locus. Each had an initial, incorrect diagnosis of ß-thalassemia trait. The correct diagnosis of NTDT was made at a mean of 7 years of age. Despite reports of this compound genotype causing NTDT, it remains unfamiliar to many clinicians. To increase awareness, we highlight its varied and sometimes subtle clinical and laboratory features and the need for comprehensive genetic testing for timely and correct diagnosis.

Lymphopenia in adults after the Fontan operation: prevalence and associations.

Lymphopenia is common in adults who have had a Fontan operation although its aetiology and clinical implications remain unknown. Previous work suggests an association between lymphopenia and both liver disease and splenomegaly. The objective of this study was to assess the prevalence of lymphopenia in adults with a Fontan circulation and evaluate its associations with risk factors and clinical outcomes. Using a retrospective cohort study design, we studied 73 adult Fontan patients (age 25.0 ± 8.4 years) who had a complete blood count and abdominal imaging performed. Patients with protein-losing enteropathy were excluded. Clinical data were extracted from hospital records. The mean white blood cell count was 6580 ± 220/ml with a mean lymphocyte count of 1223 ± 508/ml. Lymphopenia, defined as lymphocyte count <1000/ml, was present in 23 (32%) patients. Patients with lymphopenia had a lower total white blood cell count (5556 ± 2517 versus 7136 ± 1924/ml, p = 0.009) and a lower platelet count (162 ± 69 versus 208 ± 69 k/ml, p = 0.008). Lymphopenia was also associated with findings of portal hypertension, including splenomegaly (36 versus 14%, p = 0.04), varices (22 versus 6%, p = 0.04), and ascites (39 versus 14%, p = 0.02). Lymphopenia did not correlate with any cardiac imaging, haemodynamic or exercise testing variables. In conclusion, lymphopenia is common in adult Fontan patients and is associated with markers of portal hypertension. Larger studies are needed to better define the relationship between lymphopenia and clinical outcomes.

RGL2 Deficiency Impairs Human Erythropoiesis By Altering Terminal Erythroid Differentiation and Apoptosis.

DISCLOSURES: No relevant conflicts of interest to declare.

Association between diffuse myocardial fibrosis and diastolic dysfunction in sickle cell anemia.

Sickle cell anemia (SCA)-related cardiomyopathy is characterized by diastolic dysfunction and hyperdynamic features. Diastolic dysfunction portends early mortality in SCA. Diastolic dysfunction is associated with microscopic myocardial fibrosis in SCA mice, but the cause of diastolic dysfunction in humans with SCA is unknown. We used cardiac magnetic resonance measurements of extracellular volume fraction (ECV) to discover and quantify diffuse myocardial fibrosis in 25 individuals with SCA (mean age, 23 ± 13 years) and determine the association between diffuse myocardial fibrosis and diastolic dysfunction. ECV was calculated from pre- and post-gadolinium T1 measurements of blood and myocardium, and diastolic function was assessed by echocardiography. ECV was markedly increased in all participants compared with controls (0.44 ± 0.08 vs 0.26 ± 0.02, P < .0001), indicating the presence of diffuse myocardial fibrosis. Seventeen patients (71%) had diastolic abnormalities, and 7 patients (29%) met the definition of diastolic dysfunction. Participants with diastolic dysfunction had higher ECV (0.49 ± 0.07 vs 0.37 ± 0.04, P = .01) and N-terminal pro-brain natriuretic peptide (NT-proBNP; 191 ± 261 vs 33 ± 33 pg/mL, P = .04) but lower hemoglobin (8.4 ± 0.3 vs 10.9 ± 1.4 g/dL, P = .004) compared with participants with normal diastolic function. Participants with the highest ECV values (≥0.40) were more likely to have diastolic dysfunction (P = .003) and increased left atrial volume (57 ± 11 vs 46 ± 12 mL/m2, P = .04) compared with those with ECV <0.4. ECV correlated with hemoglobin (r = -0.46, P = .03) and NT-proBNP (r = 0.62, P = .001). In conclusion, diffuse myocardial fibrosis, determined by ECV, is a common and previously underappreciated feature of SCA that is associated with diastolic dysfunction, anemia, and high NT-proBNP. Diffuse myocardial fibrosis is a novel mechanism that appears to underlie diastolic dysfunction in SCA.

Robust clinical and laboratory response to hydroxyurea using pharmacokinetically guided dosing for young children with sickle cell anemia.

Hydroxyurea is FDA-approved and now increasingly used for children with sickle cell anemia (SCA), but dosing strategies, pharmacokinetic (PK) profiles, and treatment responses for individual patients are highly variable. Typical weight-based dosing with step-wise escalation to maximum tolerated dose (MTD) leads to predictable laboratory and clinical benefits, but often takes 6 to 12 months to achieve. The Therapeutic Response Evaluation and Adherence Trial (TREAT, NCT02286154) was a single-center study designed to prospectively validate a novel personalized PK-guided hydroxyurea dosing strategy with a primary endpoint of time to MTD. Enrolled participants received a single oral 20 mg/kg dose of hydroxyurea, followed by a sparse PK sampling approach with three samples collected over three hours. Analysis of individual PK data into a population PK model generated a starting dose that targets the MTD. The TREAT cohort (n = 50) was young, starting hydroxyurea at a median age of 11 months (IQR 9-26 months), and PK-guided starting doses were high (27.7 ± 4.9 mg/kg/d). Time to MTD was 4.8 months (IQR 3.3-9.3), significantly shorter than comparison studies (p < 0.0001), thus meeting the primary endpoint. More remarkably, the laboratory response for participants starting with a PK-guided dose was quite robust, achieving higher hemoglobin (10.1 ± 1.3 g/dL) and HbF (33.3 ± 9.1%) levels than traditional dosing. Though higher than traditional dosing, PK-guided doses were safe without excess hematologic toxicities. Our data suggest early initiation of hydroxyurea, using a personalized dosing strategy for children with SCA, provides laboratory and clinical response beyond what has been seen historically, with traditional weight-based dosing.

Abnormal submaximal cardiopulmonary exercise parameters predict impaired peak exercise performance in sickle cell anemia patients.

PURPOSE: Sickle cell anemia (SCA) patients frequently have many comorbidities, including diastolic dysfunction (DD) and exercise intolerance. SCA patients often cannot reach maximal effort on exercise testing; little is known regarding whether submaximal exercise parameters can predict abnormal maximal exercise results in SCA patients and if there are any possible associations with DD. METHODS: A prospective longitudinal study was performed in SCA patients. All patients had a resting cardiac MRI (CMR), cardiopulmonary exercise test (CPET) with cycle ergometry using a ramp protocol, and an echocardiogram. Exercise data were compared with age-, gender-, and size-matched normal controls. RESULTS: Compared with normal controls, the SCA group (n = 19) had lower mean max oxygen consumption (VO2 ; 1378 ± 412 mL/min vs 2237 ± 580, P < 0.01) and workload (117 ± 37.6 watts vs 175 ± 50.5 watts, P = 0.0003). When evaluating the submaximal exercise parameters, there was lower VO2 at the anaerobic threshold (AT; 950 ± 311.7 vs 1460 ± 409.9, P < 0.01) and oxygen uptake efficiency slope (OUES) at AT (1512 ± 426.2 vs 2080 ± 339, P < 0.01). The max VO2 strongly correlated with VO2 at AT (r = 0.9, P < 0.01) and OUES (r = 0.83, P < 0.01) at AT. The VO2 at AT correlated with hematocrit (r = 0.77, P < 0.05). The OUES correlated with left ventricular ejection fraction by CMR (r = 0.55, P = 0.01), hematocrit (r = 0.52, P = 0.02), and lateral E/e' (r = -0.54, P = 0.01). CONCLUSIONS: SCA patients have abnormal submaximal exercise measures compared with controls, which is strongly associated with abnormal maximal exercise results. The degree of submaximal abnormality correlates with DD abnormalities by echocardiography. These data expand the scope of functional cardiovascular abnormalities in SCA.

Sickle cell anemia mice develop a unique cardiomyopathy with restrictive physiology.

Cardiopulmonary complications are the leading cause of mortality in sickle cell anemia (SCA). Elevated tricuspid regurgitant jet velocity, pulmonary hypertension, diastolic, and autonomic dysfunction have all been described, but a unifying pathophysiology and mechanism explaining the poor prognosis and propensity to sudden death has been elusive. Herein, SCA mice underwent a longitudinal comprehensive cardiac analysis, combining state-of-the-art cardiac imaging with electrocardiography, histopathology, and molecular analysis to determine the basis of cardiac dysfunction. We show that in SCA mice, anemia-induced hyperdynamic physiology was gradually superimposed with restrictive physiology, characterized by progressive left atrial enlargement and diastolic dysfunction with preserved systolic function. This phenomenon was absent in WT mice with experimentally induced chronic anemia of similar degree and duration. Restrictive physiology was associated with microscopic cardiomyocyte loss and secondary fibrosis detectable as increased extracellular volume by cardiac-MRI. Ultrastructural mitochondrial changes were consistent with severe chronic hypoxia/ischemia and sarcomere diastolic-length was shortened. Transcriptome analysis revealed up-regulation of genes involving angiogenesis, extracellular-matrix, circadian-rhythm, oxidative stress, and hypoxia, whereas ion-channel transport and cardiac conduction were down-regulated. Indeed, progressive corrected QT prolongation, arrhythmias, and ischemic changes were noted in SCA mice before sudden death. Sudden cardiac death is common in humans with restrictive cardiomyopathies and long QT syndromes. Our findings may thus provide a unifying cardiac pathophysiology that explains the reported cardiac abnormalities and sudden death seen in humans with SCA.

Diastolic dysfunction is associated with exercise impairment in patients with sickle cell anemia.

BACKGROUND: Left ventricular diastolic dysfunction (DD) is an independent risk factor for mortality in sickle cell anemia (SCA) and is associated with increased extracellular volume (ECV) on cardiac MRI (CMR). Exercise impairment is common in SCA, but its causes and prognostic value are not well understood. OBJECTIVE: To study the effects of DD and ECV on cardiopulmonary exercise test (CPET) in patients with SCA. METHODS AND RESULTS: As part of a prospective study to characterize the cardiomyopathy of SCA (NCT02410811), 20 children and adults with SCA underwent CMR, echocardiography, and cycle ergometer CPET (age range 8-43 years). Maximum exercise was reached in 18 patients and 17 (94%) had reduced exercise capacity (%predicted VO2 less than 80%). Six patients had DD and none had systolic dysfunction. Patients with DD had lower exercise capacity compared to patients with normal diastolic function (%predicted VO2 48.2 ± 9.1% vs. 61.2 ± 11.7%; P = 0.01). The z-score of left ventricular lateral E/e' ratio, which is a marker of DD, was negatively associated with %predicted VO2 (r = -0.61, P = 0.01). All patients with moderate-to-severe exercise impairment (%predicted VO2  < 60%) had lateral E/e' z-score > 2. In a multivariate analysis, lateral E/e' z-score was independently associated with %predicted VO2 (P = 0.02). All participants had elevated ECV but the degree of elevation was not associated with exercise parameters. CONCLUSION: Left ventricular DD is associated with decreased exercise capacity in SCA. Interventions to prevent or delay DD could improve exercise capacity, quality of life, and long-term outcomes in SCA.

Applications of cardiac magnetic resonance imaging in sickle cell disease.

Cardiac magnetic resonance imaging (CMR) has evolved from an effective research tool to a non-invasive clinical modality with versatile applications. The accuracy of volume measurements and functional assessment and the ability to identify unique myocardial tissue characteristics non-invasively are the primary advantages of CMR. The use of CMR in sickle cell disease (SCD) has been limited clinically to myocardial iron assessment. The use of other CMR applications to characterize the cardiac pathology in SCD is slowly emerging but remains limited to research level. In this review, we discuss some of the applications of CMR in studying cardiovascular diseases and its potential uses in SCD for research and clinical purposes.

Losartan for the nephropathy of sickle cell anemia: A phase-2, multicenter trial.

Nephropathy is a common and progressive complication of sickle cell anemia (SCA). In SCA mice, we found that hyperangiotensinemia in the absence of hypertension underlies nephropathy, and its downregulation by losartan, an angiotensin-II-receptor-1 blocker, reduced albuminuria and progression of nephropathy. Therefore, we performed a phase-2 trial of oral losartan, given for 6 months, to explore whether it reduced albuminuria in children and adults with SCA. Participants were allocated to groups defined by class of baseline urinary albumin-to-creatinine ratio (UACR): no albuminuria (NoA), microalbuminuria (MicroA), and macroalbuminuria (MacroA). The primary endpoint was a ≥25% reduction UACR from baseline. There were 32 evaluable participants (mean age 24 years; NoA = 14, MicroA = 12, MacroA = 6). The primary endpoint was met in 83% of the MacroA group (P < 0.0001) and 58% of the MicroA group (P < 0.0001). Median fold-change in UACR was -0.74 for MacroA and -0.46 for MicroA. In MacroA and MicroA, UACR classification improved in 50% but worsened in 11%. Urine osmolality and estimated glomerular filtration rate (eGFR) did not change significantly. Losartan was discontinued in three participants [leg cramps, N = 1; decline in eGFR >25% (142➝104 mL/minute/1.73 m2 ), N = 1; rise in serum creatinine >50% (0.2➝0.3 mg/dL), N = 1]. Albuminuria was associated with diastolic dysfunction and impaired functional capacity, although cardiopulmonary status was unchanged after 6 months of losartan therapy. In summary, losartan decreased urinary albumin excretion in most participants with albuminuria. Those with macroalbuminuria had the greatest benefit. This study forms the basis for a phase-3, randomized, placebo-controlled trial of losartan for the nephropathy of SCA.

A reappraisal of the mechanisms underlying the cardiac complications of sickle cell anemia.

Anemia, hemolysis-driven vasculopathy, and intrinsic myocardial injury have been proposed as predisposing factors to cardiac disease in sickle cell anemia (SCA). The individual impact of these mechanisms on the cardiac features of SCA and the way they influence complications such as sudden death and dysrhythmias have been unclear. Recent findings of an acquired restrictive SCA-related cardiomyopathy, driven by myocardial fibrosis, may explain some of these cardiac features. Given the complexity of cardiac pathology in SCA, using additional parameters to tricuspid regurgitant jet velocity (left atrial volume, diastolic parameters, NT-proBNP) may improve the accuracy of noninvasive screening for cardiopulmonary complications in SCA.

Genotype-phenotype correlations in hereditary elliptocytosis and hereditary pyropoikilocytosis.

Hereditary elliptocytosis (HE) and hereditary pyropoikilocytosis (HPP) are heterogeneous red blood cell (RBC) membrane disorders that result from mutations in the genes encoding α-spectrin (SPTA1), ß-spectrin (SPTB), or protein 4.1R (EPB41). The resulting defects alter the horizontal cytoskeletal associations and affect RBC membrane stability and deformability causing shortened RBC survival. The clinical diagnosis of HE and HPP relies on identifying characteristic RBC morphology on peripheral blood smear and specific membrane biomechanical properties using osmotic gradient ektacytometry. However, this phenotypic diagnosis may not be readily available in patients requiring frequent transfusions, and does not predict disease course or severity. Using Next-Generation sequencing, we identified the causative genetic mutations in fifteen patients with clinically suspected HE or HPP and correlated the identified mutations with the clinical phenotype and ektacytometry profile. In addition to identifying three novel mutations, gene sequencing confirmed and, when the RBC morphology was not evaluable, identified the diagnosis. Moreover, genotypic differences justified the phenotypic differences within families with HE/HPP.

Biochemical surrogate markers of hemolysis do not correlate with directly measured erythrocyte survival in sickle cell anemia.

Hemolysis is a key feature of sickle cell anemia (HbSS). Direct quantitation of hemolysis could be used as an objective outcome in clinical trials of new therapeutics for HbSS and would also enable better human studies of the pathogenesis of complications of HbSS that are ostensibly hemolysis-related, such as pulmonary hypertension. However, contemporary human studies in HbSS have used only surrogate markers of hemolysis rather than direct measurements of RBC survival. We directly quantified hemolysis in HbSS by measuring survival of an age cohort of RBCs labeled with a stable isotope, administered orally as 15 N-glycine, a metabolic precursor of heme. The atomic excess of 15 N in heme extracted from blood was monitored by mass spectrometry over time. We performed 13 labeling experiments in 11 individuals with HbSS. Mean RBC survival was 31.9 days (range 14.1-53.6). Both HbF level, a known determinant of hemolysis, and absolute reticulocyte count (ARC), an index of the marrow's response to hemolysis, correlated with directly measured RBC survival (r = 0.61, P < 0.002; r = -0.84, P < 0.001). However, commonly used biochemical surrogates of hemolysis (LDH, AST, bilirubin, and plasma free hemoglobin) did not correlate with directly measured RBC survival. These biochemical surrogates should be interpreted cautiously, at best, in clinical trials and human physiologic studies in HbSS. ARC was the best correlate of total hemolysis, but only 70% of the variation in RBC survival was reflected in this marker. If greater accuracy is required in human studies, 15 N-glycine RBC labeling can directly and accurately quantify hemolysis. Am. J. Hematol. 91:1195-1201, 2016. © 2016 Wiley Periodicals, Inc.