The paradox of hemoglobin SC disease

An Unusual Compound Heterozygosity for Hb O-Arab (HBB: c.364G>A) and Hb D-Los Angeles (HBB: c.364G>C)

We report a newborn with a compound heterozygosity for Hb O-Arab (HBB: 364G>A) and Hb D-Los Angeles (HBB: 364G>C). To the best of our knowledge, the combination of these two hemoglobin (Hb) variants has not been identified and reported before. The variants of the proband and parents were identified by high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). DNA analysis was performed to confirm the variants. The levels of Hb variants of the proband were determined post-partum, at 3 months and 1 year after birth. Blood count analysis after 1 year revealed that the proband had a mild microcytic anemia. Furthermore, HPLC and CE analysis revealed an equal distribution of Hb D-Los Angeles compared to Hb O-Arab at the age of 1 year. The follow-up of the patient, suggested that the Hb combination is clinically silent or mild.

Dengue in hospitalized children with sickle cell disease: A retrospective cohort study in the French departments of America

BACKGROUND

To describe the characteristics of dengue in sickle cell children and try to identify risk factors of severity.

METHODS

In this retrospective study, we describe the evolution according to genotype (SS or SC and controls) and severity.

RESULTS AND CONCLUSIONS

From 2005 to 2013, 106 hospitalizations for dengue fever were recorded, 35 SS genotype, 35 SC and 36 without SCD or any other chronic disease. The clinical evolution was quite different. During hospitalization, SC patients were more likely to develop multiorgan failure (31.4% versus 25.7% for SS, and 0% for controls, p=0.001), or acute pulmonary complications than patients without SC sickle cell disease (14.3% versus 8.6% for SS, and 0% for controls, p=0.03). Level 3 analgesic treatment was more frequent in SC patients (22.9% versus 3% for SS, and 0% for controls, p<0.001). Patients with SC sickle cell disease had a higher proportion of severe forms of dengue (57.1% versus 37.1% for SS, and 0% for controls, p<0.001) than patients without SC sickle cell disease. Transfer in intensive care unit was required for most SC patients (22.9% versus 3% for SS, and 0% for controls, p=0.005).Fatal episodes were more frequent in SC patients than in patients without SC sickle cell disease (5 deaths versus 1 for SS and 0 for controls, p=0.02). Thirty-three patients (47.1%) were diagnosed as having severe dengue (13 SS and 20 SC). On univariate analysis, age >10 years, acute pulmonary complications, multiorgan failure, severe anemia requiring transfusion, use of antibiotic treatment, need for treatment with morphine, and longer hospital stay were statistically more frequent in severe dengue-associated cases. Multiple logistic regression analysis showed that HbSC genotype and acute pulmonary complications, were significantly associated with severe dengue. In the multivariate model, the area of the ROC curve was 0.831. Children with SC genotype, typically thought to have less severe disease, actually had a higher rate of severe dengue and death than those with SS genotype.

Total Serum Magnesium Levels and Calcium-To-Magnesium Ratio in Sickle Cell Disease

Background and objectives: Imbalance of calcium/magnesium ratio could lead to clinical complications in sickle cell disease (SCD). Low levels of magnesium have been associated with sickling, increased polymerization and vaso-occlusion (VOC) in sickle cell due to cell dehydration. The K-Cl cotransport plays a very important role in sickle cell dehydration and is inhibited by significantly increasing levels of magnesium. The study evaluated total serum magnesium levels and computed calcium/magnesium ratio in SCD patients and "healthy" controls. Materials and methods: The study was a case-control cross-sectional one, involving 120 SCD patients (79 Haemoglobin SS (HbSS)and 41 Haemoglobin SC (HbSC)) at the steady state and 48 "healthy" controls. Sera were prepared from whole blood samples (n = 168) and total magnesium and calcium measured using a Flame Atomic Absorption Spectrometer (Variant 240FS manufactured by VARIAN Australia Pty Ltd., Melbourne, VIC, Australia). Calcium/magnesium ratios were calculated in patients and the controls. Results: The prevalence of hypomagnesemia and hypocalcaemia among the SCD patients was observed to be 39.17% and 52.50% respectively, higher than the controls (4.17% and 22.92%, for hypomagnesemia and hypocalcaemia, respectively). Level of magnesium was significantly lower in the SCD patients compared to their healthy counterparts (p = 0.002). The magnesium level was further reduced in the HbSS patients but not significantly different from the HbSC patients (p = 0.584). calcium/magnesium ratio was significantly higher in the SCD patients (p = 0.031). Although calcium/magnesium ratio was higher in the HbSC patients compared to those with the HbSS genotype, the difference was not significant (p = 0.101). Conclusion: The study shows that magnesium homeostasis are altered in SCD patients, and their levels are lower in HbSS patients. Although calcium/magnesium ratio is significantly higher in SCD patients compared with controls, there is no significant difference between patients with HbSS and HbSC genotypes. Magnesium supplementation may be required in sickle cell patients.

TTP-like syndrome associated with hemoglobin SC disease treated successfully with plasma and red cell exchange

Background

Sickle cell hemoglobinopathies are associated with end organ damage but very rarely present with a clinical and laboratory picture of microangiopathic hemolytic anemia (MAHA) and thrombocytopenia, characteristic of thrombotic microangiopathy (TMA).

Case presentation

We present a patient with HbSC disease who developed thrombotic microangiopathy, needing both RBC exchange transfusion and therapeutic plasma exchange (TPE) for complete clinical recovery.

Conclusion

Although literature showed therapeutic plasma exchange alone can abrogate a similar clinical scenario, we did an in-depth review which concluded that in most of the TMA cases secondary to sickle cell disease, treatment with both with plasma exchange and red cell exchange transfusion are necessary.

Multifocal electroretinogram findings in sickle cell maculopathy

BACKGROUND

The aim of the present work was to describe and compare multifocal electroretinogram findings (mfERG) between patients with sickle cell disease (SCD) without clinical sign of maculopathy and controls (HbAA).

METHODS

Both HbSS (homozygous SCD) and HbSC (compound heterozygous SCD) patients, the two most frequent SCD genotypes, were included. All individuals underwent a full ophthalmologic examination (with a fundoscopy), a spectral domain ocular coherence tomography (SD-OCT) and a mfERG.

RESULTS

A total of 86 subjects were included: 54 SCD patients (107 eyes) with 32 HbSS (63 eyes) and 22 HbSC (44 eyes) and 32 controls (64 eyes). None of the eyes showed retinal clinical abnormalities. SD-OCT analysis showed that macular thickness was statistically lower in SCD eyes than in controls. mfERG analysis demonstrated a significant reduction of N1 (initial-negative deflection), and P1 (positive peak) response amplitude densities of HbSS eyes compared to HbAA eyes from the centre (<2°) and to the periphery (>15°). Implicit time response was also reduced in the centre (<2°). N1 and P1 response amplitude densities of HbSC eyes were significantly lower than those of HbAA eyes from the centre (<2°) to the periphery (>15°). N1 implicit time was statistically reduced in HbSS compared to HbSC eyes.

CONCLUSION

Our study is the first one to describe macular electrophysiological dysfunction in SCD patients. Moreover, we confirm that SCD maculopathy is equally frequent in HbSS and HbSC.

Effectiveness of hydroxycarbamide in children with sickle cell disease - Analysis of dose-response metrics in a large birth cohort in a tertiary sickle cell centre

BACKGROUND

Despite the well-established efficacy of hydroxycarbamide in the management of sickle cell disease (SCD), the paucity of real-world clinical data limits the establishment of a practical dosing strategy. The aim of this study was to analyse the dose-response metrics of hydroxycarbamide associated with the minimum effective dose protocol - specifically, between dose groups and differing degrees of myelosuppression.

DESIGN/METHODS

A retrospective cohort study was conducted on 93 patients who were initiated on hydroxycarbamide between 2005 and 2017 at a tertiary haemoglobinopathy centre in London, UK. The burden of acute SCD-related complications was defined by the annualised rates of emergency department attendances and hospital admissions. Secondary outcomes included haematological, biochemical, liver, renal and transcranial Doppler velocity status. Comparisons were performed upon stratification via dose (<20 mg/kg/day, 20-24 mg/kg/day and ≥25 mg/kg/day) and sustained absolute neutrophil count (ANC) values (ANC <4 × 10⁹ /L and ANC ≥4 × 10⁹ /L).

RESULTS

Clinical outcomes were not predicted by dose or ANC values. Whilst laboratory indices between dose groups were also non-statistically significant, patients maintained on ANC <4 × 10⁹ /L were shown to achieve superior responses in haemoglobin, haemoglobin F, absolute reticulocyte count and liver function. Toxicities occurred idiosyncratically, with minimal reports of transient neutropaenia and thrombocytopaenia.

CONCLUSIONS

Objective clinical responses may be achievable without intensive dose escalation. Our finding that greater myelosuppression is associated with greater improvements in laboratory markers of clinical benefit is consistent with prior clinical trials, but ongoing effectiveness studies are needed to determine whether these benefits can be reliably demonstrated in routine clinical practice using different dosing protocols.

Sickle cell disease: Clinical presentation and management of a global health challenge

Sickle cell disease is an autosomal recessive, multisystem disorder, characterised by chronic haemolytic anaemia, painful episodes of vaso-occlusion, progressive organ failure and a reduced life expectancy. Sickle cell disease is the most common monogenetic disease, with millions affected worldwide. In well-resourced countries, comprehensive care programs have increased life expectancy of sickle cell disease patients, with almost all infants surviving into adulthood. Therapeutic options for sickle cell disease patients are however, still scarce. Predictors of sickle cell disease severity and a better understanding of pathophysiology and (epi)genetic modifiers are warranted and could lead to more precise management and treatment. This review provides an extensive summary of the pathophysiology and management of sickle cell disease and encompasses the characteristics, complications and current and future treatment options of the disease.

Rapid and reproducible characterization of sickling during automated deoxygenation in sickle cell disease patients

In sickle cell disease (SCD), sickle hemoglobin (HbS) polymerizes upon deoxygenation, resulting in sickling of red blood cells (RBCs). These sickled RBCs have strongly reduced deformability, leading to vaso‐occlusive crises and chronic hemolytic anemia. To date, there are no reliable laboratory parameters or assays capable of predicting disease severity or monitoring treatment effects. We here report on the oxygenscan, a newly developed method to measure RBC deformability (expressed as Elongation Index ‐ EI) as a function of pO₂. Upon a standardized, 22 minute, automated cycle of deoxygenation (pO₂ median 16 mmHg ± 0.17) and reoxygenation, a number of clinically relevant parameters are produced in a highly reproducible manner (coefficients of variation <5%). In particular, physiological modulators of oxygen affinity, such as, pH and 2,3‐diphosphoglycerate showed a significant correlation (respectively R = ‑0.993 and R = 0.980) with Point of Sickling (PoS_5%), which is defined as the pO₂ where a 5% decrease in EI is observed during deoxygenation. Furthermore, in vitro treatment with antisickling agents, including GBT440, which alter the oxygen affinity of hemoglobin, caused a reproducible left‐shift of the PoS, indicating improved deformability at lower oxygen tensions. When RBCs from 21 SCD patients were analyzed, we observed a significantly higher PoS in untreated homozygous SCD patients compared to treated patients and other genotypes. We conclude that the oxygenscan is a state‐of‐the‐art technique that allows for rapid analysis of sickling behavior in SCD patients. The method is promising for personalized treatment, development of new treatment strategies and could have potential in prediction of complications.

Misdiagnosis: Acute Chest Syndrome That Evolved into Acute Respiratory Distress Syndrome in a Patient without a Documented History of Hemoglobinopathy

Acute chest syndrome (ACS) is a feared complication of sickle cell disease. Here is a case of a patient who presented with symptoms suggestive of acute chest syndrome yet had a delayed diagnosis presumably due to the lack of documented history of sickle cell disease of the patient, consequently evolving into acute respiratory distress syndrome (ARDS). He was subsequently diagnosed with heterozygous sickle cell SC disease on hemoglobin electrophoresis. After appropriate management with mechanical ventilator, broad-spectrum empiric intravenous antibiotics, exchange transfusion, and intravenous fluid resuscitation, the patient was medically optimized and safely discharged home, with significant improvement noted on successive follow-up visits.

Elevated fetal haemoglobin levels are associated with decreased incidence of retinopathy in adults with sickle cell disease

Among the many vascular complications of sickle cell disease (SCD), retinopathy is the most prevalent and represents a leading cause of blindness. Hydroxycarbamide therapy ameliorates many symptoms of SCD, and high fetal haemoglobin (HbF) levels have been shown to protect against the development of retinopathy in children with HbSS. Its effect on adults with SCD, who are at a much higher risk of developing retinopathy, has not been studied. We aimed to investigate the effect of hydroxycarbamide use and HbF level on sickle cell retinopathy development in adults. We performed a retrospective cross-sectional study and collected demographics, comorbidities, and ocular and haematological data from 300 adult sickle cell subjects examined at the Henkind Eye Institute at Montefiore Medical Center during a 5-year period, from October 2012 to November 2017. The cohort was comprised mainly of Black and Hispanic subjects with all SCD genotypes, aged 18-71 years. Results show that in HbSS patients treated with hydroxycarbamide, those with retinopathy had significantly lower HbF levels compared to patients without retinopathy (P = 0·018). Our study identified the optimal HbF cut-off point for retinopathy protection to be 14·87%. Thus, a HbF level of 15% appears to be the threshold above which the odds for developing retinopathy in SS patients are reduced by 50%.

Clinical and hematological profile in a newborn cohort with hemoglobin SC

OBJECTIVES

Hemoglobin SC is the second most common variant of sickle-cell disease worldwide, after hemoglobin SS. The objectives of the study were to describe the clinical and laboratory characteristics of hemoglobin SC disease in children from a newborn screening program and treated at a blood center.

METHODOLOGY

This study assessed a cohort of 461 infants born between 01/01/1999 and 12/31/2012 and followed-up until 12/31/2014. Clinical events were expressed as rates for 100 patient-years, with 95% confidence intervals. Kaplan-Meier survival curves were created.

RESULTS

The median age of patients was 9.2 years; 47.5% were female. Mean values of blood tests were: hemoglobin, 10.5g/dL; reticulocytes, 3.4%; white blood cells, 11.24×10⁹/L; platelets, 337.1×10⁹/L; and fetal hemoglobin, 6.3%. Clinical events: acute splenic sequestration in 14.8%, blood transfusion 23.4%, overt stroke in 0.2%. The incidence of painful vaso-occlusive episodes was 51 (48.9-53.4) per 100 patient-years and that of infections, 62.2 episodes (59.8-64.8) per 100 patient-years. Transcranial Doppler ultrasonography (n=71) was normal given the current reference values for SS patients. Hydroxyurea was given to ten children, all of whom improvement of painful crises. Retinopathy was observed in 20.3% of 59 children who underwent ophthalmoscopy. Avascular necrosis was detected in seven of 12 patients evaluated, predominantly in the left femur. Echocardiogram compatible with pulmonary hypertension was recorded in 4.6% of 130 children, with an estimated average systolic pulmonary artery pressure of 33.5mmHg. The mortality rate from all causes was 4.3%.

CONCLUSIONS

Clinical severity is variable in SC hemoglobinopathy. Several children have severe manifestations similar to those with SS disease.

Herbal Drug use in Sickle Cell Disease Management; Trends and Perspectives in Sub-Saharan Africa - A Systematic Review

INTRODUCTION

Nigeria has the largest burden of Sickle Cell Disease (SCD) with estimated 100,000 new born affected annually. SCD is a Hemoglobin (Hb) disorder with the major form resulting from the substitution of a polar glutamate (Glu) by non-polar Valine (Val) in an invariant region of Hbβ chain-subunit. Species of Hb found in the sickle cell trait are HbA and HbS in a 60:40 proportion, in SCD only HbS, in the HbC disease only HbC, and in the SC disease it's HbS and HbC in a 50:50 equal proportion.

OBJECTIVE

This paper reviews herbal medicines usage in sub-Saharan Africa (sSA) to ameliorate the crisis associated with SCD. The model Hb tetramer suggests a higher membrane affinity of HbS and HbC, promoting dehydration of RBCs, with concomitant in vivo crystallization. Some drawbacks using these herbal drugs include; poor bioavailability and the lack of proper pharmacovigilance monitoring procedures arising from weak governance structure combined with under reporting of herbal usage to physicians were discussed. Probable epigenetic loci that could be targeted using phytomedicines for effective SCD management were also discussed.

METHODS

Using search engines, several databases including Google scholar, PubMed, Academic Resource Index were utilized as a source for relevant publications/ literature. The protein coordinates for the Hb tetramer were obtained from the Protein Data Bank (PDB).

CONCLUSION

Manipulation of epigenetics to achieve better SCD management involves careful thinking. Herein, we discuss some epigenetic interactions that could be putatively tweaked with a view of enhancing soluble bioactive small molecular components with the potential to reactivate γ -globin genes, thereby boosting immune response in patient with SCD.

Diagnostic accuracy in field conditions of the sickle SCAN® rapid test for sickle cell disease among children and adults in two West African settings: the DREPATEST study

Background

Sickle cell disease (SCD) accounts for 5% of mortality in African children aged < 5 years. Improving the care management and quality of life of patients with SCD requires a reliable diagnosis in resource-limited settings. We assessed the diagnostic accuracy of the rapid Sickle SCAN® point-of-care (POC) test for SCD used in field conditions in two West-African countries.

Methods

We conducted a case-control study in Bamako (Mali) and Lomé (Togo). Known cases of sickle cell disease (HbSS, HbSC), trait (HbAS), HbC heterozygotes (HbAC) and homozygous (HbCC), aged ≥6 months were compared to Controls (HbAA), recruited by convenience. All subjects received both an index rapid POC test and a gold standard (high-performance liquid chromatography in Bamako; capillary electrophoresis in Lomé). Personnel conducting tests were blinded from subjects' SCD status. Sensitivity and specificity were calculated for each phenotype. Practicality was assessed by local healthcare professionals familiar with national diagnostic methods and their associated constraints.

Results

In Togo, 209 Cases (45 HbAS, 39 HbAC, 41 HbSS, 44 HbSC and 40 HbCC phenotypes) were compared to 86 Controls (HbAA). 100% sensitivity and specificity were observed for AA Controls and HbCC cases. Estimated sensitivity was 97.7% [95% confidence interval: 88.0-99.9], 97.6% [87.1-99.9%], 95.6% [84.8-99.5%], and 94.9% [82.7-99.4], for HbSC, HbSS, HbAS, and HbAC, respectively. Specificity exceeded 99.2% for all phenotypes. Among 160 cases and 80 controls in Mali, rapid testing was 100% sensitive and specific. Rapid testing was well accepted by local healthcare professionals.

Conclusion

Rapid POC testing is 100% accurate for homozygote healthy people and excellent (Togo) or perfect (Mali) for sickle cell trait and disease patients. In addition to its comparable diagnostic performance, this test is cheaper, easier to implement, and logistically more convenient than the current standard diagnostic methods in use. Its predictive value indicators and diagnostic accuracy in newborns should be further evaluated prior to implementation in large-scale screening programs in resource-limited settings where SCD is prevalent.

Differences in heme and hemopexin content in lipoproteins from patients with sickle cell disease

BACKGROUND

High blood cholesterol is associated with atherogenesis and endothelial dysfunction. The latter is present in hemolytic diseases, such as sickle cell anemia, whose carriers have hypocholesterolemia and low incidence of coronary artery disease.

OBJECTIVE

We aimed to characterize cholesterol fractions in patients with sickle cell disease and explore the relationship among lipoproteins, varying degrees of hemolysis, and its biomarkers.

METHODS

We recruited 37 healthy individuals, 39 with hemoglobin SC disease, and 40 with sickle cell anemia and quantified cholesterol fractions, heme resulting from hemoglobin breakdown, and its main scavenger protein hemopexin.

RESULTS

Hypocholesterolemia was most significant in patients with sickle cell anemia, and cholesterol levels correlated positively with hemopexin. Nevertheless, patients still had higher relative low-density lipoprotein (LDL) oxidation than healthy subjects. Analysis of lipoproteins isolated by density ultracentrifugation showed that the LDL fraction contained higher concentrations of heme than the high-density lipoprotein (HDL) fraction, whereas HDL contained more hemopexin than LDL, albeit greatly reduced in patients.

CONCLUSION

Our findings show that the abnormally low lipoprotein levels in sickle cell anemia correlate with hemolysis markers, particularly with hemopexin concentrations, along with significant reduction of this heme scavenger in HDL fractions. This may suggest an important role for HDL in the defense against heme-induced endothelial dysfunction in hemolytic diseases.

Red Blood Cell Disorders: Perioperative Considerations for Patients Undergoing Cardiac Surgery

Disorders affecting red blood cells (RBCs) are uncommon yet have many important physiologic considerations for patients undergoing cardiac surgery. RBC disorders can be categorized by those that are congenital or acquired, and further by disorders affecting the RBC membrane, hemoglobin, intracellular enzymes, or excessive RBC production. A foundational understanding of the physiologic derangement for these disorders is critical when considering perioperative implications and optimization, strategies for cardiopulmonary bypass, and the rapid recognition and treatment if complications occur. This review systematically outlines the RBC disorders of frequency and relevance with an emphasis on how the disorder affects normal physiologic processes, a review of the literature related to the disorder, and the implications and recommendations for patients undergoing cardiac surgery.

Inflammation in sickle cell disease

The primary β-globin gene mutation that causes sickle cell disease (SCD) has significant pathophysiological consequences that result in hemolytic events and the induction of the inflammatory processes that ultimately lead to vaso-occlusion. In addition to their role in the initiation of the acute painful vaso-occlusive episodes that are characteristic of SCD, inflammatory processes are also key components of many of the complications of the disease including autosplenectomy, acute chest syndrome, pulmonary hypertension, leg ulcers, nephropathy and stroke. We, herein, discuss the events that trigger inflammation in the disease, as well as the mechanisms, inflammatory molecules and cells that propagate these inflammatory processes. Given the central role that inflammation plays in SCD pathophysiology, many of the therapeutic approaches currently under pre-clinical and clinical development for the treatment of SCD endeavor to counter aspects or specific molecules of these inflammatory processes and it is possible that, in the future, we will see anti-inflammatory drugs being used either together with, or in place of, hydroxyurea in those SCD patients for whom hematopoietic stem cell transplants and evolving gene therapies are not a viable option.

Massive Ovarian Edema in a Girl with Hemoglobin SC Disease

Massive ovarian edema is a benign tumor like lesion of the ovary. The widely accepted mechanism is disruption of vascular drainage resulting in accumulation of fluid within the stroma and enlargement of the ovary. We report a case of massive ovarian edema in a teenage girl with hemoglobin SC disease. A 16-year-old female with hemoglobin SC disease was admitted with right lower quadrant pain. An ultrasound and CT scan showed a large, heterogeneous solid, and cystic pelvic mass. Due to the size and the possibility of malignancy, the patient underwent a salpingo-oophorectomy. The mass was an 8.3 cm hemorrhagic cyst with some solid areas. Histologic exam showed diffuse edema with scattered entrapped follicles and a narrow rim of normal appearing ovarian stroma. Dilated and occluded capillaries were seen along with hemorrhage and sickled red blood cells but no necrosis was identified. These histologic features were consistent with massive ovarian edema. Massive ovarian edema is thought to be caused by disturbance of the vascular outflow resulting in fluid buildup in the stroma. It is most often attributed to intermittent ovarian torsion that disrupts capillary and venous flow, but arterial flow is maintained. Rare cases of massive ovarian edema caused by tumor emboli or external compression by tumors have been reported, but this is the first case of a patient with hemoglobin SC disease developing vasoocclusions resulting in this lesion.

High body mass index in children with sickle cell disease: a retrospective single-centre audit

OBJECTIVE

To assess the prevalence of high body mass index (BMI) in children with sickle cell disease and assess correlation between BMI and disease severity.

DESIGN

Retrospective chart review followed by statistical analysis.

SETTING

A single tertiary paediatric clinic in inner city London.

PATIENTS

All patients with sickle cell disease, including homozygous haemoglobin (HbSS) and compound heterozygous Hb (HbSC), age 2-18 years receiving clinical care at the centre, were included in the study.

INTERVENTIONS

Height and weight measurements, steady-state laboratory blood tests, hospital admission rates, adjunct therapy such as hydroxycarbamide or blood transfusions and obstructive sleep apnoea (OSA) data were obtained from the hospital electronic patient records.

MAIN OUTCOME MEASURES

To study the prevalence of high BMI and to identify any correlation between BMI and disease severity.

RESULTS

385 patients were included. 64 children (17%) were overweight or obese, of which a significantly higher number of children with HbSC were obese or overweight (23 out of 91, 25%) compared with those with HbSS (36 out of 273, 13%), p≤0.001. No correlation was found between high BMI and presence of OSA, and markers of disease severity such as admission rates, fetal haemoglobin or lactate dehydrogenase levels.

CONCLUSIONS

High BMI did not correlate with disease severity in this cohort of patients with sickle cell disease. Obesity was more prevalent in females and those with HbSC. Further prospective studies are needed to determine long-term effects of BMI in disease severity and outcome.

Bone marrow necrosis and fat embolism syndrome: a dreadful complication of hemoglobin sickle cell disease

Sickle cell disease encompasses a wide range of genotypic presentation with particular clinical features. The entity affects millions of people, particularly those whose ancestors came from sub-Saharan Africa and other countries in the Western Hemisphere, Saudi Arabia, and India. Currently, the high frequency of S and C genes reflects natural selection through the protection of heterozygotes against severe malaria, the high frequency of consanguineous marriages, improvement of some public health policies and the nutritional standards in the poorer countries where newborns are now living long enough to present for diagnosis and management. Although there is a high burden of the disease, in many countries, the new-born sickle cell screening test is being performed and is rendering an early diagnosis; however, it is still difficult for sickle cell patients to find proper treatment and adequate follow-up. Moreover, in many countries, patients are neither aware of their diagnosis nor the care they should receive to prevent complications; also, they do not receive adequate genetic counseling. Hemoglobin SC (HbSC) disease is the most frequent double sickle cell heterozygosis found in Brazil. The clinical course tends to be more benign with fewer hospitalizations compared with double homozygotic SS patients. However, HbSC patients may present severe complications with a fatal outcome. We report the case of a 36-year-old man who presented to the emergency care facility with symptoms consistent with the diagnosis of sickling crisis. The outcome was unfavorable and death occurred just hours after admission. The autopsy revealed a generalized vaso-occlusive crisis by sickled red cells, bone marrow necrosis, and fat embolism syndrome.

HbS-Sicilian (δβ)0-Thalassemia: A Rare Variant of Sickle Cell

Sickle cell disease (SCD) is caused by a mutation in the sixth codon of the β-globin gene on chromosome 11, which leads to a single amino acid substitution (glutamine to valine). Sickle-(δβ)⁰-thalassemia is a rare variant of sickle cell disease (delta-beta thalassemia occurring in association with sickle hemoglobin, HbS), sparsely reported in literature, and has been associated with symptomatology necessitating careful monitoring and follow-up. We describe a patient who presented with a newborn screen reported as “FS” and a negative family history for sickle cell disease and sickle cell trait. Subsequent gene sequencing studies demonstrated the presence of Sickle-(δβ)⁰-thalassemia. Clinical course has remained relatively stable for this patient now at 18 months of age without any SCD related symptomatology or complications. As this is a rare variant of SCD with potential complications, it is important to establish diagnosis towards planning comprehensive care.

Central sensitization associated with low fetal hemoglobin levels in adults with sickle cell anemia

BACKGROUND AND AIMS

Pain is the hallmark of sickle cell anemia (SCA), presenting as recurrent acute events or chronic pain. Central sensitization, or enhanced excitability of the central nervous system, alters pain processing and contributes to the maintenance of chronic pain. Individuals with SCA demonstrate enhanced sensitivity to painful stimuli however central mechanisms of pain have not been fully explored. We hypothesized that adults with SCA would show evidence of central sensitization as observed in other diseases of chronic pain.

METHODS

We conducted a prospective study of static and dynamic quantitative sensory tests in 30 adults with SCA and 30 matched controls.

RESULTS

Static thermal testing using cold stimuli showed lower pain thresholds (p=0.04) and tolerance (p=0.04) in sickle cell subjects, but not for heat. However, SCA subjects reported higher pain ratings with random heat pulses (p<0.0001) and change in scores with temporal summation at the heat pain threshold (p=0.002). Similarly, with the use of pressure pain stimuli, sickle cell subjects reported higher pain ratings (p=0.04), but not higher pressure pain tolerance/thresholds or allodynia to light tactile stimuli. Temporal summation pain score changes using 2 pinprick probes (256 and 512mN) were significantly greater (p=0.004 and p=0.008) with sickle cell, and delayed recovery was associated with lower fetal hemoglobin (p=0.002 and 0.003).

CONCLUSIONS

Exaggerated temporal summation responses provide evidence of central sensitization in SCA.

IMPLICATIONS

The association with fetal hemoglobin suggests this known SCA modifier may have a therapeutic role in modulating central sensitization.

Substituting Sodium Hydrosulfite with Sodium Metabisulfite Improves Long-Term Stability of a Distributable Paper-Based Test Kit for Point-of-Care Screening for Sickle Cell Anemia

Sickle cell anemia (SCA) is a genetic blood disorder that is particularly lethal in early childhood. Universal newborn screening programs and subsequent early treatment are known to drastically reduce under-five SCA mortality. However, in resource-limited settings, cost and infrastructure constraints limit the effectiveness of laboratory-based SCA screening programs. To address this limitation our laboratory previously developed a low-cost, equipment-free, point-of-care, paper-based SCA test. Here, we improved the stability and performance of the test by replacing sodium hydrosulfite (HS), a key reducing agent in the hemoglobin solubility buffer which is not stable in aqueous solutions, with sodium metabisulfite (MS). The MS formulation of the test was compared to the HS formulation in a laboratory setting by inexperienced users (n = 3), to determine visual limit of detection (LOD), readout time, diagnostic accuracy, intra- and inter-observer agreement, and shelf life. The MS test was found to have a 10% sickle hemoglobin LOD, 21-min readout time, 97.3% sensitivity and 99.5% specificity for SCA, almost perfect intra- and inter-observer agreement, at least 24 weeks of shelf stability at room temperature, and could be packaged into a self-contained, distributable test kits comprised of off-the-shelf disposable components and food-grade reagents with a total cost of only $0.21 (USD).

Laboratory and Genetic Biomarkers Associated with Cerebral Blood Flow Velocity in Hemoglobin SC Disease

Reference values for cerebral blood flow velocity (CBFV) in hemoglobin SC disease (HbSC) have not been established. We aimed to investigate associations between laboratory and genetic biomarkers associated with CBFV in HbSC children. Sixty-eight HbSC children were included; CBFV was analyzed by transcranial Doppler, and the time-averaged maximum mean velocity (TAMMV) was estimated. Hematological, biochemical, immunological, and genetic analyses were performed. TAMMV was negatively correlated with red blood cell count (RBC) count, hemoglobin, hematocrit, and direct bilirubin (DB), yet positively correlated with monocytes and ferritin. We found that children with TAMMV ≥ 128 cm/s had decreased red blood cell distribution width (RDW) and nitric oxide metabolite (NOx) concentration. Children with TAMMV ≥ 143.50 cm/s had decreased hemoglobin and hematocrit, as well as increased ferritin levels. Decreased hemoglobin, hematocrit, RDW, and NOx and increased ferritin were detected in children with TAMMV ≥ 125.75 cm/s. The CAR haplotype was associated with higher TAMMV. In association analyses, RBC, hemoglobin, hematocrit, RDW, monocyte, DB, NOx, and ferritin, as well as the CAR haplotype, were found to be associated with higher TAMMV in HbSC children. Multivariate analysis suggested that high TAMMV was independently associated with hematocrit, RDW, and NOx. Additional studies are warranted to validate the establishment of a cutoff value of 125.75 cm/s associated with elevated TAMMV in HbSC children.

The super sickling haemoglobin HbS-Oman: a study of red cell sickling, K+ permeability and associations with disease severity in patients heterozygous for HbA and HbS-Oman (HbA/S-Oman genotype)

Studying different sickle cell genotypes may throw light on the pathogenesis of sickle cell disease (SCD). Here, the clinical profile, red cell sickling and K⁺ permeability in 29 SCD patients (15 patients with severe disease and 14 with a milder form) of HbA/S-Oman genotype were analysed. The super sickling nature of this Hb variant was confirmed. The red cell membrane permeability to K⁺ was markedly abnormal with elevated activities of P_sickle , Gardos channel and KCl cotransporter (KCC). Results were consistent with Ca²⁺ entry and Mg²⁺ loss via P_sickle stimulating Gardos channel and KCC activities. The abnormal red cell behaviour was similar to that in the commonest genotype of SCD, HbSS, in which the level of mutated Hb is considerably higher. Although activities of all three K⁺ transporters also correlated with the level of HbS-Oman, there was no association between transport phenotype and disease severity. The super sickling behaviour of HbS-Oman may obviate the need for solute loss and red cell dehydration to encourage Hb polymerisation, required in other SCD genotypes. Disease severity was reduced by concurrent α thalassaemia, as observed in other SCD genotypes, and represents an obvious genetic marker for prognostic tests of severity in young SCD patients of the HbA/S-Oman genotype.

[Fortuitous detection of composite heterozygous S/C sickle cell disease]

Le syndrome drépanocytaire composite SC représente 20% à 30% des syndromes drépanocytaires majeurs. Nous rapportons le cas d'une découverte fortuite d'une drépanocytose hétérozygote composite SC dans un contexte de décollement rétinien. Il s'agit d'une patiente hospitalisée au service d'ophtalmologie pour une baisse de l'acuité visuelle détectée depuis 06 mois et rebelle au traitement. Les antécédents cliniques sont dominés par la mise en place d'une prothèse totale de la hanche (PTH) douze ans auparavant. Notre observation rappelle la grande variabilité clinique de la maladie drépanocytaire imposant un dépistage précoce des patients à risque avec une surveillance clinique adaptée afin d'éviter l'évolution vers des séquelles organiques irréversibles telles que la rétinopathie drépanocytaire.

Hemoglobin Variant Profiles among Brazilian Quilombola Communities

Brazilian Quilombolas are communities composed of African-derived populations that have their territories guaranteed by the Brazilian Constitution. The present study investigated the hemoglobin (Hb) variants among these population groups. This study was conducted in a total of 2843 individuals of Brazilian Quilombola communities of the Bahia, Pará, and Piauí states. All the participants had their Hb profiles evaluated. The Hb S (HBB: c.20A>T) variant was described in all the studied localities. However, the individuals in Bahia State had the highest frequency of the Hb C (HBB: c.19G>A) variant; individuals from Piauí State had a higher frequency of the Hb D-Punjab (HBB: c.364G>C) variant compared to the other states, and individuals from Pará State only carried the Hb S variant. The present study revealed a specific distribution of Hb variants that could represent different waves of African influence in these Brazilian populations.

Differences of microparticle patterns between sickle cell anemia and hemoglobin SC patients

Sickle cell anemia (SCA) and hemoglobin SC (HbSC) disease are the two most common forms of sickle cell disease (SCD), a frequent hemoglobinopathy which exhibits a highly variable clinical course. Although high levels of microparticles (MPs) have been consistently reported in SCA and evidence of their harmful impact on the SCA complication occurrences have been provided, no data on MP pattern in HbSC patients has been reported so far. In this study, we determined and compared the MP patterns of 84 HbSC and 96 SCA children, all at steady-state, using flow cytometry. Most of circulating MPs were derived from platelets (PLTs) and red blood cells (RBCs) in the two SCD syndromes. Moreover, we showed that HbSC patients exhibited lower blood concentration of total MPs compared to SCA patients, resulting mainly from a decrease of MP levels originated from RBCs and to a lesser extent from PLTs. We did not detect any association between blood MP concentrations and the occurrence of painful vaso-occlusive crises, acute chest syndrome and pulmonary hypertension in both patient groups. We also demonstrated for the first time, that whatever the considered genotype, RBC-derived MPs exhibited higher externalized phosphatidylserine level and were larger than PLT-derived MPs.

Stroke in a Child with Hemoglobin SC Disease: A Case Report Describing use of Hydroxyurea after Transfusion Therapy

Children with hemoglobin SC (HbSC) disease suffer a significant incidence of silent cerebral infarcts but stroke is rare. A 2-year-old African American boy with HbSC disease presented with focal neurologic deficits associated with magnetic resonance imaging evidence of cerebral infarction with vascular abnormalities. After the acute episode he was treated with monthly transfusions and subsequently transitioned to hydroxyurea therapy. The benefits of hydroxyurea as a fetal hemoglobin inducer in HbSC disease, to ameliorate clinical symptoms are supported by retrospective studies. This case highlights the rare occurrence of stroke in a child with HbSC disease and the use of hydroxyurea therapy.

Blood transfusion for preventing primary and secondary stroke in people with sickle cell disease

BACKROUND

Sickle cell disease is one of the commonest severe monogenic disorders in the world, due to the inheritance of two abnormal haemoglobin (beta globin) genes. Sickle cell disease can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Stroke affects around 10% of children with sickle cell anaemia (HbSS). Chronic blood transfusions may reduce the risk of vaso-occlusion and stroke by diluting the proportion of sickled cells in the circulation.This is an update of a Cochrane Review first published in 2002, and last updated in 2013.

OBJECTIVES

To assess risks and benefits of chronic blood transfusion regimens in people with sickle cell disease for primary and secondary stroke prevention (excluding silent cerebral infarcts).

SEARCH METHODS

We searched for relevant trials in the Cochrane Library, MEDLINE (from 1946), Embase (from 1974), the Transfusion Evidence Library (from 1980), and ongoing trial databases; all searches current to 04 April 2016.We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Haemoglobinopathies Trials Register: 25 April 2016.

SELECTION CRITERIA

Randomised controlled trials comparing red blood cell transfusions as prophylaxis for stroke in people with sickle cell disease to alternative or standard treatment. There were no restrictions by outcomes examined, language or publication status.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility and the risk of bias and extracted data.

MAIN RESULTS

We included five trials (660 participants) published between 1998 and 2016. Four of these trials were terminated early. The vast majority of participants had the haemoglobin (Hb)SS form of sickle cell disease.Three trials compared regular red cell transfusions to standard care in primary prevention of stroke: two in children with no previous long-term transfusions; and one in children and adolescents on long-term transfusion.Two trials compared the drug hydroxyurea (hydroxycarbamide) and phlebotomy to long-term transfusions and iron chelation therapy: one in primary prevention (children); and one in secondary prevention (children and adolescents).The quality of the evidence was very low to moderate across different outcomes according to GRADE methodology. This was due to the trials being at a high risk of bias due to lack of blinding, indirectness and imprecise outcome estimates. Red cell transfusions versus standard care Children with no previous long-term transfusionsLong-term transfusions probably reduce the incidence of clinical stroke in children with a higher risk of stroke (abnormal transcranial doppler velocities or previous history of silent cerebral infarct), risk ratio 0.12 (95% confidence interval 0.03 to 0.49) (two trials, 326 participants), moderate quality evidence.Long-term transfusions may: reduce the incidence of other sickle cell disease-related complications (acute chest syndrome, risk ratio 0.24 (95% confidence interval 0.12 to 0.48)) (two trials, 326 participants); increase quality of life (difference estimate -0.54, 95% confidence interval -0.92 to -0.17) (one trial, 166 participants); but make little or no difference to IQ scores (least square mean: 1.7, standard error 95% confidence interval -1.1 to 4.4) (one trial, 166 participants), low quality evidence.We are very uncertain whether long-term transfusions: reduce the risk of transient ischaemic attacks, Peto odds ratio 0.13 (95% confidence interval 0.01 to 2.11) (two trials, 323 participants); have any effect on all-cause mortality, no deaths reported (two trials, 326 participants); or increase the risk of alloimmunisation, risk ratio 3.16 (95% confidence interval 0.18 to 57.17) (one trial, 121 participants), very low quality evidence. Children and adolescents with previous long-term transfusions (one trial, 79 participants)We are very uncertain whether continuing long-term transfusions reduces the incidence of: stroke, risk ratio 0.22 (95% confidence interval 0.01 to 4.35); or all-cause mortality, Peto odds ratio 8.00 (95% confidence interval 0.16 to 404.12), very low quality evidence.Several review outcomes were only reported in one trial arm (sickle cell disease-related complications, alloimmunisation, transient ischaemic attacks).The trial did not report neurological impairment, or quality of life. Hydroxyurea and phlebotomy versus red cell transfusions and chelationNeither trial reported on neurological impairment, alloimmunisation, or quality of life. Primary prevention, children (one trial, 121 participants)Switching to hydroxyurea and phlebotomy may have little or no effect on liver iron concentrations, mean difference -1.80 mg Fe/g dry-weight liver (95% confidence interval -5.16 to 1.56), low quality evidence.We are very uncertain whether switching to hydroxyurea and phlebotomy has any effect on: risk of stroke (no strokes); all-cause mortality (no deaths); transient ischaemic attacks, risk ratio 1.02 (95% confidence interval 0.21 to 4.84); or other sickle cell disease-related complications (acute chest syndrome, risk ratio 2.03 (95% confidence interval 0.39 to 10.69)), very low quality evidence. Secondary prevention, children and adolescents (one trial, 133 participants)Switching to hydroxyurea and phlebotomy may: increase the risk of sickle cell disease-related serious adverse events, risk ratio 3.10 (95% confidence interval 1.42 to 6.75); but have little or no effect on median liver iron concentrations (hydroxyurea, 17.3 mg Fe/g dry-weight liver (interquartile range 10.0 to 30.6)); transfusion 17.3 mg Fe/g dry-weight liver (interquartile range 8.8 to 30.7), low quality evidence.We are very uncertain whether switching to hydroxyurea and phlebotomy: increases the risk of stroke, risk ratio 14.78 (95% confidence interval 0.86 to 253.66); or has any effect on all-cause mortality, Peto odds ratio 0.98 (95% confidence interval 0.06 to 15.92); or transient ischaemic attacks, risk ratio 0.66 (95% confidence interval 0.25 to 1.74), very low quality evidence.

AUTHORS' CONCLUSIONS

There is no evidence for managing adults, or children who do not have HbSS sickle cell disease.In children who are at higher risk of stroke and have not had previous long-term transfusions, there is moderate quality evidence that long-term red cell transfusions reduce the risk of stroke, and low quality evidence they also reduce the risk of other sickle cell disease-related complications.In primary and secondary prevention of stroke there is low quality evidence that switching to hydroxyurea with phlebotomy has little or no effect on the liver iron concentration.In secondary prevention of stroke there is low-quality evidence that switching to hydroxyurea with phlebotomy increases the risk of sickle cell disease-related events.All other evidence in this review is of very low quality.

Kinetic assay shows that increasing red cell volume could be a treatment for sickle cell disease

Although it has been known for more than 60 years that the cause of sickle cell disease is polymerization of a hemoglobin mutant, hydroxyurea is the only drug approved for treatment by the US Food and Drug Administration. This drug, however, is only partially successful, and the discovery of additional drugs that inhibit fiber formation has been hampered by the lack of a sensitive and quantitative cellular assay. Here, we describe such a method in a 96-well plate format that is based on laser-induced polymerization in sickle trait cells and robust, automated image analysis to detect the precise time at which fibers distort ("sickle") the cells. With this kinetic method, we show that small increases in cell volume to reduce the hemoglobin concentration can result in therapeutic increases in the delay time prior to fiber formation. We also show that, of the two drugs (AES103 and GBT440) in clinical trials that inhibit polymerization by increasing oxygen affinity, one of them (GBT440) also inhibits sickling in the absence of oxygen by two additional mechanisms.

Genetic Basis and Genetic Modifiers of β-Thalassemia and Sickle Cell Disease

β-thalassemia and sickle cell disease (SCD) are prototypical Mendelian single gene disorders, both caused by mutations affecting the adult β-globin gene. Despite the apparent genetic simplicity, both disorders display a remarkable spectrum of phenotypic severity and share two major genetic modifiers-α-globin genotype and innate ability to produce fetal hemoglobin (HbF, α₂γ₂).This article provides an overview of the genetic basis for SCD and β-thalassemia, and genetic modifiers identified through phenotype correlation studies. Identification of the genetic variants modifying HbF production in combination with α-globin genotype provide some prediction of disease severity for β-thalassemia and SCD but generation of a personalized genetic risk score to inform prognosis and guide management requires a larger panel of genetic modifiers yet to be discovered.Nonetheless, genetic studies have been successful in characterizing some of the key variants and pathways involved in HbF regulation, providing new therapeutic targets for HbF reactivation.

Knowledge insufficient: the management of haemoglobin SC disease

Although haemoglobin SC (HbSC) accounts for 30% of sickle cell disease (SCD) in the United States and United Kingdom, evidence-based guidelines for genotype specific management are lacking. The unique pathology of HbSC disease is complex, characterized by erythrocyte dehydration, intracellular sickling and increased blood viscosity. The evaluation and treatment of patients with HbSC is largely inferred from studies of SCD consisting mostly of haemoglobin SS (HbSS) patients. These studies are underpowered to allow definitive conclusions about HbSC. We review the pathophysiology of HbSC disease, including known and potential differences between HbSS and HbSC, and highlight knowledge gaps in HbSC disease management. Clinical and translational research is needed to develop targeted treatments and to validate management recommendations for efficacy, safety and impact on quality of life for people with HbSC.

Spinal Cord Infarction in Hemoglobin SC Disease as an Amusement Park Accident

Spinal cord infarction (SCI) is extremely rare in children, and only 2 other reports have described the occurrence of SCI in patients with hemoglobin SC disease (HbSC). Amusement park accidents are serious injuries. Patients with preexisting conditions, such as hypertension, cardiac disease, and recent back or neck injuries, may be at an increased risk. We report the case of a 12-year-old girl with HbSC with a past history of only 2 admissions for pain crises, who presented to the emergency department with symptoms of SCI after riding a roller coaster. Fibrocartilaginous embolism (FCE) is an increasingly recognized cause of SCI after events that put strain on the axial skeleton, such as many amusement park rides. Although radiologic criteria for FCE have been proposed, FCE remains a diagnosis of exclusion. To the best of our knowledge, this is the first documented case of SCI in a patient with HbSC and the first case of FCE after an amusement park accident. This case report highlights that HbSC may confound the differential diagnosis of SCI and aims to document an association with FCE in pediatric patients.

Differential time-dependent volumetric and surface area changes and delayed induction of new permeation pathways in P. falciparum-infected hemoglobinopathic erythrocytes

During intraerythrocytic development, Plasmodium falciparum increases the ion permeability of the erythrocyte plasma membrane to an extent that jeopardizes the osmotic stability of the host cell. A previously formulated numeric model has suggested that the parasite prevents premature rupture of the host cell by consuming hemoglobin (Hb) in excess of its own anabolic needs. Here, we have tested the colloid‐osmotic model on the grounds of time‐resolved experimental measurements on cell surface area and volume. We have further verified whether the colloid‐osmotic model can predict time‐dependent volumetric changes when parasites are grown in erythrocytes containing the hemoglobin variants S or C. A good agreement between model‐predicted and empirical data on both infected erythrocyte and intracellular parasite volume was found for parasitized HbAA and HbAC erythrocytes. However, a delayed induction of the new permeation pathways needed to be taken into consideration for the latter case. For parasitized HbAS erythrocyte, volumes diverged from model predictions, and infected erythrocytes showed excessive vesiculation during the replication cycle. We conclude that the colloid‐osmotic model provides a plausible and experimentally supported explanation of the volume expansion and osmotic stability of P. falciparum‐infected erythrocytes. The contribution of vesiculation to the malaria‐protective function of hemoglobin S is discussed.

A hypothesis of target cell formation in sickle cell disease

A fraction of erythrocytes appear as target cells in stained blood smears in sickle cell disease, due to a inheritance of the hemoglobin variant Hb S, polymerizing upon deoxygenation. These cells appear in a three dimension as thin cups. A process of their formation in this disease is proposed based on a band 3-based mechanism of the erythrocyte shape control, able to explain the erythrocyte echinocytosis by glucose depletion. It indicates that their formation is due to a stomatocytogenic slow outward transport of the dibasic form of endogenous Pi with an H(+) by band 3, promoted by the decrease of the Donnan ratio, which decreases cell pH and volume, attributed by a decrease of cell KCl concentration by the higher efflux of K(+)Cl(-) cotransport and Ca(2+) activation of the Gardos channel. Its implications are briefly discussed with respect to target cells per se, target cell formation in other hemoglobinopathies, acquired and inherited disorders of the lipid metabolism and dehydrated hereditary stomatocytosis as well as a stomatocyte presence in a double heterozygote of Hb S and Hb C and of an involvement of the process of target cell formation in acanthocytosis in acquired and inherited disorders.

Original Research: Use of hydroxyurea and phlebotomy in pediatric patients with hemoglobin SC disease

Hydroxyurea is an excellent therapeutic agent for the pharmacological induction of HbF in patients with sickle cell disease (SCD). However, all completed clinical trials of hydroxyurea have excluded patients with hemoglobin SC (HbSC) disease. HbSC differs significantly in pathophysiology from HbSS, as HbC does not sickle, but instead causes cellular dehydration which potentiates sickling of HbS. Many severely affected HbSC patients have been placed on hydroxyurea on a case by case basis, but there are no large scale prospective data on safety or efficacy of hydroxyurea in this subset of patients with SCD. Here, we report a case series of 14 pediatric patients with HbSC treated to maximum tolerated dose (MTD) with hydroxyurea. Those who failed to show clinical improvement after at least six months at MTD were offered phlebotomy in addition to hydroxyurea. Five out of 11 patients with HbSC who achieved MTD failed to demonstrate clinical improvement on hydroxyurea. Of the four placed on dual hydroxyurea and phlebotomy therapy, all showed at least partial clinical improvement. Percent dense red blood cells (%DRBC) were measured via an ADVIA hematology analyzer. A marked rise in percent dense cells preceded clinical complications in three patients. Dual therapy with hydroxyurea and phlebotomy may be an effective approach to patients with HbSC that do not experience improvement with hydroxyurea alone. Monitoring of %DRBC may predict adverse events and aid in assessing hydroxyurea compliance. Large scale clinical trials are needed to evaluate the safety and efficacy of hydroxyurea and hydroxyurea with phlebotomy in patients with HbSC disease.

Acute Splenic Sequestration Crisis in a 70-Year-Old Patient With Hemoglobin SC Disease

A 70-year-old African American female with a past medical history significant for chronic bilateral shoulder pain and reported sickle cell trait presented with acute-onset bilateral thoracolumbar pain radiating to her left arm. Two days after admission, Hematology was consulted for severely worsening microcytic anemia and thrombocytopenia. Examination of the patient's peripheral blood smear from admission revealed no cell sickling, spherocytes, or schistocytes. Some targeting was noted. A Coombs test was negative. The patient was eventually transferred to the medical intensive care unit in respiratory distress. Hemoglobin electrophoresis confirmed a diagnosis of hemoglobin SC disease. A diagnosis of acute splenic sequestration crisis complicated by acute chest syndrome was crystallized, and red blood cell exchange transfusion was performed. Further research is necessary to fully elucidate the pathophysiology behind acute splenic sequestration crisis, and the role of splenectomy to treat hemoglobin SC disease patients should be better defined.

Hemoglobin to Hematocrit Ratio: The Strongest Predictor of Femoral Head Osteonecrosis in Children With Sickle Cell Disease

BACKGROUND

Femoral head osteonecrosis (ON) secondary to sickle cell disease (SCD) often progresses to femoral head collapse, requiring total hip arthroplasty. However, this treatment has a limited durability and patients with SCD have higher rates of complications, requiring multiple revision operations. Identifying risk factors linked to ON in SCD can facilitate earlier precollapse diagnosis and surgical treatment aimed at preservation of the native hip joint.

METHODS

Fifty-nine children treated at our institution between January 2001 and April 2012 with SCD and ON, as diagnosed by magnetic resonance imaging or radiographic imaging, were compared with age-matched and sickle cell phenotype-matched (SS, SC, Sβ, Sβ) controls with no evidence of ON. Two sided t-tests assuming unequal variances determined statistically risk factors and threshold values were assigned to calculate odds ratios.

RESULTS

Systolic blood pressure (P=1.2×10, OR=3.68), diastolic blood pressure (P=0.0084, OR=1.41), weight in the SCD-SS population (P=0.04, OR=1.85), and hemoglobin (Hb) in the SCD-SS population (P=0.036, OR=2.56) were elevated in cases. Curiously, dividing the Hb by the hematocrit to serve as a clinical proxy for the mean corpuscular Hb concentration (MCHC) produced an excellent predictor of ON (P=2.06×10, OR=5.17), which was especially pronounced in the SCD-SS subpopulation (P=2.28×10, OR=8.65). Among children with SCD, the overall prevalence of ON was 9% (59/658) and the phenotype with the highest prevalence of ON was Sβ thalassemia with an ON prevalence of 11.1%. There was no observed correlation between ON and height, body mass index, cholesterol, mean corpuscular volume, hematocrit, or glucocorticoid use.

CONCLUSIONS

These data support a novel clinical marker, the MCHC proxy, as the strongest predictor of ON in children with SCD. High-risk children should receive hip magnetic resonance imaging to diagnose early ON and facilitate interventions focused on hip preservation, forestalling, or possibly preventing, the need for total hip arthroplasty.

Screening for Structural Hemoglobin Variants in Bahia, Brazil

Brazil was the country that received the largest number of Africans during the time of colonization, and Bahia was the Brazilian state that received the largest number of slaves from Africa. The purpose of this study was to evaluate the coverage of the newborn screening program for sickle cell disease in the Recôncavo Baiano region of the state of Bahia, and to show the frequency of the subjects with hemoglobin variants in the 2006–2009 period. Blood samples from neonates in twelve cities in the Recôncavo Baiano region were analyzed by High Performance Liquid Chromatography. A total of 16,402 children were born in this period, 14,773 of which underwent newborn screening. In this period 1416 children were born carrying hemoglobin variants HbS and HbC. Forty-seven patients—20 HbSS genotype and 27 HbSC genotype—were diagnosed in eleven of the twelve cities surveyed. The proportion of children born with sickle cell disease in the Recôncavo Baiano region was 1/314, which was higher than the 1/650 rate for the state of Bahia. The data presented in this study confirm the high frequency of sickle cell disease in Recôncavo Baiano, demonstrating the need to create a referral center for the care of patients with sickle cell diseases in the region.

Effects of hydroxyurea treatment for patients with hemoglobin SC disease

Although hemoglobin SC (HbSC) disease is usually considered less severe than sickle cell anemia (SCA), which includes HbSS and HbS/β(0) -thalassemia genotypes, many patients with HbSC experience severe disease complications, including vaso-occlusive pain, acute chest syndrome, avascular necrosis, retinopathy, and poor quality of life. Fully 20 years after the clinical and laboratory efficacy of hydroxyurea was proven in adult SCA patients, the safety and utility of hydroxyurea treatment for HbSC patients remain unclear. Recent NHLBI evidence-based guidelines highlight this as a critical knowledge gap, noting HbSC accounts for ∼30% of sickle cell patients within the United States. To date, only 5 publications have reported short-term, incomplete, or conflicting laboratory and clinical outcomes of hydroxyurea treatment in a total of 71 adults and children with HbSC. We now report on a cohort of 133 adult and pediatric HbSC patients who received hydroxyurea, typically for recurrent vaso-occlusive pain. Hydroxyurea treatment was associated with a stable hemoglobin concentration; increased fetal hemoglobin (HbF) and mean corpuscular volume (MCV); and reduced white blood cell count (WBC), absolute neutrophil count (ANC), and absolute reticulocyte count (ARC). Reversible cytopenias occurred in 22% of patients, primarily neutropenia and thrombocytopenia. Painful events were reduced with hydroxyurea, more in patients >15 years old. These multicenter data support the safety and potentially salutary effects of hydroxyurea treatment for HbSC disease; however, a multicenter, placebo-controlled, Phase 3 clinical trial is needed to determine if hydroxyurea therapy has efficacy for patients with HbSC disease.

Sickle haemoglobin, haemoglobin C and malaria mortality feedbacks

BACKGROUND

Sickle haemoglobin (HbS) and haemoglobin C (HbC) are both caused by point mutations in the beta globin gene, and both offer substantial malaria protection. Despite the fact that the blood disorder caused by homozygosity for HbC is much less severe than that caused by homozygosity for HbS (sickle cell anaemia), it is the sickle mutation which has come to dominate many old-world malarious regions, whilst HbC is highly restricted in its geographical distribution. It has been suggested that this discrepancy may be due to sickle cell heterozygotes enjoying a higher level of malaria protection than heterozygotes for HbC. A higher fitness of sickle cell heterozygotes relative to HbC heterozygotes could certainly have allowed the sickle cell allele to spread more rapidly. However, observations that carrying either HbC or HbS enhances an individual's capacity to transmit malaria parasites to mosquitoes could also shed light on this conundrum.

METHODS

A population genetic model was used to investigate the evolutionary consequences of the strength of malaria selection being correlated with either HbS frequency or HbC frequency.

RESULTS

If the selection pressure from malaria is positively correlated with the frequency of either HbS or HbC, it is easier for HbS to succeed in the competitive interaction between the two alleles.

CONCLUSIONS

A feedback process whereby the presence of variant haemoglobins increases the level of malaria selection in a population could have contributed to the global success of HbS relative to HbC, despite the former's higher blood disorder cost.

Validation of a Low-Cost Paper-Based Screening Test for Sickle Cell Anemia

Background

The high childhood mortality and life-long complications associated with sickle cell anemia (SCA) in developing countries could be significantly reduced with effective prophylaxis and education if SCA is diagnosed early in life. However, conventional laboratory methods used for diagnosing SCA remain prohibitively expensive and impractical in this setting. This study describes the clinical validation of a low-cost paper-based test for SCA that can accurately identify sickle trait carriers (HbAS) and individuals with SCA (HbSS) among adults and children over 1 year of age.

Methods and Findings

In a population of healthy volunteers and SCA patients in the United States (n = 55) the test identified individuals whose blood contained any HbS (HbAS and HbSS) with 100% sensitivity and 100% specificity for both visual evaluation and automated analysis, and detected SCA (HbSS) with 93% sensitivity and 94% specificity for visual evaluation and 100% sensitivity and 97% specificity for automated analysis. In a population of post-partum women (with a previously unknown SCA status) at a primary obstetric hospital in Cabinda, Angola (n = 226) the test identified sickle cell trait carriers with 94% sensitivity and 97% specificity using visual evaluation (none of the women had SCA). Notably, our test permits instrument- and electricity-free visual diagnostics, requires minimal training to be performed, can be completed within 30 minutes, and costs about $0.07 in test-specific consumable materials.

Conclusions

Our results validate the paper-based SCA test as a useful low-cost tool for screening adults and children for sickle trait and disease and demonstrate its practicality in resource-limited clinical settings.