Variability of homozygous sickle cell disease: The role of alpha and beta globin chain variation and other factors

Introduction to Special Issue: Genomic Analysis of Common Disease

The development of NextGen or massive parallel sequencing [...].

Newborn Screening for Sickle Cell Disease: Results from a Pilot Study in the Portuguese Population

The Portuguese Newborn Screening Program currently includes 28 pathologies: congenital hypothyroidism, cystic fibrosis, 24 inborn errors of metabolism, sickle cell disease and spinal muscular atrophy. This pilot study for sickle cell disease newborn screening, including 188,217 samples, was performed between May 2021 and December 2023, with phase I, including 24,130 newborns, in the Lisbon and Setubal districts and phase II, including 164,087 newborns, in the whole country. DBS samples were analyzed through capillary electrophoresis. In phase I, a high birth incidence of sickle cell disease was found (1:928 NBs), resulting from the identification of 24 HbSS and 2 HbSC patients. This birth incidence decreased but remained significant when the pilot study for sickle cell disease newborn screening was expanded to a national level, with the identification of 67 sickle cell disease patients (59 HbSS and 8 HbSC), revealing a birth incidence of 1:2449 NBs. These data suggest that this condition is becoming increasingly relevant in Portugal, thus reflecting a general European trend, where sickle cell disease is already recognized as a public health problem. Therefore, it highlights the importance of its integration into the Portuguese National Newborn Screening Program panel in January 2024, thus allowing the early identification and clinical follow-up of these patients.

Sickle Cell Anemia and Inflammation: A Review of Stones and Landmarks Paving the Road in the Last 25 Years

A quarter of a century ago, sickle cell disease (SCD) was mainly viewed as a typical genetic disease inherited as a classical Mendelian trait. Therefore, the main focus concerning SCD was on diagnosis, meaning, genotyping, and identification of homozygous and heterozygous individuals carrying the relevant HbS mutant allele. Nowadays, it is well established that sickle cell disease is indeed the result of homozygosis for the HbS variant, although this single feature is not capable of explaining the highly diverse clinical presentation of SCD. In fact, an important feature of SCD is the chronic inflammation that accompanies the sickling of erythrocytes. In this manuscript, we will revisit the early evidence of inflammation in SCD and review what was uncovered during the last 25 years. Here, we describe Sickle cell anemia as a major participant in the history of science. In fact, SCD was the first genetic disease where the causal mutation was identified and is also the first disease for which treatment through genome editing was approved, making this disease a landmark in the road of molecular biology.

A moonlighting job for α-globin in blood vessels

ABSTRACT

Red blood cells express high levels of hemoglobin A tetramer (α2β2) to facilitate oxygen transport. Hemoglobin subunits and related proteins are also expressed at lower levels in other tissues across the animal kingdom. Physiological functions for most nonerythroid globins likely derive from their ability to catalyze reduction-oxidation (redox) reactions via electron transfer through heme-associated iron. An interesting example is illustrated by the recent discovery that α-globin without β-globin is expressed in some arteriolar endothelial cells (ECs). α-globin binds EC nitric oxide (NO) synthase (eNOS) and degrades its enzymatic product NO, a potent vasodilator. Thus, depletion of α-globin in ECs or inhibition of its association with eNOS causes arteriolar relaxation and lowering of blood pressure in mice. Some of these findings have been replicated in isolated human blood vessels, and genetic studies are tractable in populations in which α-thalassemia alleles are prevalent. Two small studies identified associations between loss of α-globin genes in humans and NO-regulated vascular responses elicited by local hypoxia-induced blood flow or thermal stimulation. In a few larger population-based studies, no associations were detected between loss of α-globin genes and blood pressure, ischemic stroke, or pulmonary hypertension. In contrast, a significant positive association between α-globin gene copy number and kidney disease was detected in an African American cohort. Further studies are required to define comprehensively the expression of α-globin in different vascular beds and ascertain their overall impact on normal and pathological vascular physiology.

Sickle Cell Disease in Brazil: Current Management

Sickle cell disease (SCD) comprises inherited red blood cell disorders due to a mutation in the β-globin gene (c20A > T, pGlu6Val) and is characterized by the presence of abnormal hemoglobin, hemoglobin S, hemolysis, and vaso-occlusion. This mutation, either in a homozygous configuration or in compound states with other β-globin mutations, leads to polymerization of hemoglobin S in deoxygenated conditions, causing modifications in red blood cell shape, particularly sickling. Vaso-occlusive crisis (VOC) is the hallmark of the disease, but other severe complications may arise from repeated bouts of VOCs. SCD is considered a global health problem, and its incidence has increased in some areas of the world, particularly the Americas and Africa. Management of the disease varies according to the region of the world, mainly due to local resources and socioeconomic status. This review aimed to describe more recent data on SCD regarding available treatment options, especially in Brazil. New treatment options are expected to be available to all patients, particularly crizanlizumab, which is already approved in the country.

CETP gene polymorphisms and haplotypes are explanatory variables for HDL cholesterol level in sickle cell disease

Variations in lipid profile have been observed in sickle cell disease (SCD) and understanding their relationship with disease severity is crucial. This study aimed to investigate the association of polymorphisms of the CETP gene and laboratory markers of disease severity with lipid profile in a pediatric population with SCD. Biochemical and anthropometric analyses and CETP and alpha-thalassemia genotyping were performed. The study included 133 children and adolescents with sickle cell anemia (SCA) or hemoglobin SC disease (SCC), in steady-state. The SCA and no hydroxyurea (no HU) groups had higher values of ApoB, total cholesterol, low-density lipoprotein cholesterol (LDL-C), and non-high-density lipoprotein cholesterol (non-HDL-C) compared to the SCC and HU groups. However, there were no significant differences in ApoA1 and HDL-C levels between the groups based on genotype. Furthermore, the groups with altered levels of ApoA1, HDL-C, and the triglyceride/HDL ratio exhibited lower hemoglobin (Hb) levels and higher white blood cell counts. Hb level was associated to HDL-C levels. Analysis of CETP gene variants showed that the minor alleles of rs3764261 (C>A), rs247616 (C>T), and rs183130 (C>T), as well as the TTA haplotype, are explanatory variables for HDL-C levels. These findings suggested that dyslipidemia in SCD, specifically related to HDL-C levels, may be influenced by individual genetic background. Additionally, further investigation is needed to determine if clinical manifestations are impacted by CETP gene variants.

A Clinical Qualification Protocol Highlights Overlapping Genomic Influences and Neuro-Autonomic Mechanisms in Ehlers-Danlos and Long COVID-19 Syndromes

A substantial fraction of the 15% with double-jointedness or hypermobility have the traditionally ascertained joint-skeletal, cutaneous, and cardiovascular symptoms of connective tissue dysplasia and its particular manifestation as Ehlers-Danlos syndrome (EDS). The holistic ascertainment of 120 findings in 1261 EDS patients added neuro-autonomic symptoms like headaches, muscle weakness, brain fog, chronic fatigue, dyspnea, and bowel irregularity to those of arthralgia and skin laxity, 15 of these symptoms shared with those of post-infectious SARS-CoV-2 (long COVID-19). Underlying articulo-autonomic mechanisms guided a clinical qualification protocol that qualified DNA variants in 317 genes as having diagnostic utility for EDS, six of them identical (F2-LIFR-NLRP3-STAT1-T1CAM1-TNFRSF13B) and eighteen similar to those modifying COVID-19 severity/EDS, including ADAMTS13/ADAMTS2-C3/C1R-IKBKG/IKBKAP-PIK3C3/PIK3R1-POLD4/POLG-TMPRSS2/TMPRSS6-WNT3/WNT10A. Also, contributing to EDS and COVID-19 severity were forty and three genes, respectively, impacting mitochondrial functions as well as parts of an overlapping gene network, or entome, that are hypothesized to mediate the cognitive-behavioral, neuro-autonomic, and immune-inflammatory alterations of connective tissue in these conditions. The further characterization of long COVID-19 natural history and genetic predisposition will be necessary before these parallels to EDS can be carefully delineated and translated into therapies.

Leg Ulcers in Sickle Cell Disease: A Multifactorial Analysis Highlights the Hemolytic Profile

Sickle cell disease (SCD) is characterized by the presence of the variant S hemoglobin (HbS). The homozygous genotype (HbSS) is sickle cell anemia (SCA), while the double heterozygous of HbS and HbC (HbSC) is defined as SC hemoglobinopathy. The pathophysiology is based on chronic hemolysis, inflammation, endothelial dysfunction, and vaso-occlusion, which results in vasculopathy and serious clinical manifestations. Sickle leg ulcers (SLUs) are cutaneous lesions around the malleoli frequent in 20% of Brazilian patients with SCD. SLUs present a variable clinical and laboratory pattern modulated by several characteristics that are not fully understood. Hence, this study aimed to investigate laboratory biomarkers and genetic and clinical parameters associated with the development of SLUs. This descriptive cross-sectional study included 69 SCD patients, 52 without SLU (SLU-) and 17 with active or previous SLU history (SLU+). The results showed a higher incidence of SLU in SCA patients and there was no observed association of α-3.7 Kb thalassemia in SLU occurrence. Alterations in NO metabolism and hemolysis were associated with clinical evolution and severity of SLU, in addition to hemolysis modulating the etiology and recurrence of SLU. Our multifactorial analyses demonstrate and extend the role of hemolysis driving the pathophysiological mechanism of SLU.

Deferasirox versus deferoxamine in managing iron overload in patients with Sickle Cell Anaemia: a systematic review and meta-analysis

OBJECTIVES

To examine the efficacy of deferasirox (DFX) by comparison with deferoxamine (DFO) in managing iron overload in patients with sickle cell anaemia (SCA).

METHODS

Online databases were systematically searched for studies published from January 2007 to July 2022 that had investigated the efficacy of DFX compared with DFO in managing iron overload in patients with SCA.

RESULTS

Of the 316 articles identified, three randomized clinical trials met the inclusion criteria. Meta-analysis of liver tissue iron concentration (LIC) showed that iron overload was not significantly higher in the DFX group compared with DFO group (WMD, -1.61 mg Fe/g dw (95% CI -4.42 to 1.21). However, iron overload as measured by serum ferritin was significantly lower in DFO compared with DFX group (WMD, 278.13 µg/l (95% CI 36.69 to 519.57). Although meta-analysis was not performed on myocardial iron concentration due to incomplete data, the original report found no significant difference between DFX and DFO.

CONCLUSION

While limited by the number of studies included in this meta-analysis, overall, the results tend to show that DFX was as effective as DFO in managing iron overload in patients with SCA.

Sickle cell disease and pregnancy profile of complicated malaria in 982 pregnancies in Kinshasa

Introduction

Malaria is associated with high morbidity during pregnancy. Homozygous sickle cell pregnant women are even more exposed during complicated malaria. The objective of the study was to evaluate the maternal and fetal morbidity of homozygous sickle cell pregnant pregnant women with complicated malaria.

Methods

We conducted a retrospective case-control study of 982 pregnancies in sickle cell pregnant women, during which a group of sickle cell pregnant women who received antimalarial chemoprophylaxis was compared to another group without chemoprophylaxis. We analyzed the clinical evolution of pregnant women (VOCs and transfusions, pregnancy weight gain) and parasite (parasite density at the time of diagnosis of complicated malaria and during treatment for three days). We analyzed the parameters of newborns at birth (age of pregnancy at the time of delivery, birth weight, weight of the placenta and histopathological examination of the placenta.

Results

Out of 982 pregnancies, 15% of pregnant women suffered from complicated malaria, 57% suffered from uncomplicated malaria and 28% did not suffer from malaria. Pregnancy weight gain, birth weight, was better in the group of pregnant women who received chemoprophylaxis and the placenta had less histological lesions. Parasite density was low. There was a significant positive correlation between parasite density and the number of CVOs and transfusions and between parasite density and histological lesions of the placenta and low birth weight.

Conclusion

Complicated malaria is associated with high maternal and fetal morbidity in sickle cell patients. Malaria chemoprophylaxis can reduce maternal and fetal complications and parasite density during malaria infection.

Determinants of severity in sickle cell disease

Sickle cell disease is a very variable condition, with outcomes ranging from death in childhood to living relatively symptom free into the 8^th decade. Much of this variability is unexplained. The co-inheritance of α thalassaemia and factors determining HbF levels significantly modify the phenotype, but few other significant genetic variants have been identified, despite extensive studies. Environmental factors are undoubtedly important, with socio-economics and access to basic medical care explaining the huge differences in outcomes between many low- and high-income countries. Exposure to cold and windy weather seems to precipitate acute complications in many people, although these effects are unpredictable and vary with geography. Many studies have tried to identify prognostic factors which can be used to predict outcomes, particularly when applied in infancy. Overall, low haemoglobin, low haemoglobin F percentage and high reticulocytes in childhood are associated with worse outcomes, although again these effects are fairly weak and inconsistent.

A polygenic score for acute vaso-occlusive pain in pediatric sickle cell disease

Individuals with monogenic disorders can experience variable phenotypes that are influenced by genetic variation. To investigate this in sickle cell disease (SCD), we performed whole-genome sequencing (WGS) of 722 individuals with hemoglobin HbSS or HbSβ0-thalassemia from Baylor College of Medicine and from the St. Jude Children's Research Hospital Sickle Cell Clinical Research and Intervention Program (SCCRIP) longitudinal cohort study. We developed pipelines to identify genetic variants that modulate sickle hemoglobin polymerization in red blood cells and combined these with pain-associated variants to build a polygenic score (PGS) for acute vaso-occlusive pain (VOP). Overall, we interrogated the α-thalassemia deletion -α3.7 and 133 candidate single-nucleotide polymorphisms (SNPs) across 66 genes for associations with VOP in 327 SCCRIP participants followed longitudinally over 6 years. Twenty-one SNPs in 9 loci were associated with VOP, including 3 (BCL11A, MYB, and the β-like globin gene cluster) that regulate erythrocyte fetal hemoglobin (HbF) levels and 6 (COMT, TBC1D1, KCNJ6, FAAH, NR3C1, and IL1A) that were associated previously with various pain syndromes. An unweighted PGS integrating all 21 SNPs was associated with the VOP event rate (estimate, 0.35; standard error, 0.04; P = 5.9 × 10-14) and VOP event occurrence (estimate, 0.42; standard error, 0.06; P = 4.1 × 10-13). These associations were stronger than those of any single locus. Our findings provide insights into the genetic modulation of VOP in children with SCD. More generally, we demonstrate the utility of WGS for investigating genetic contributions to the variable expression of SCD-associated morbidities.

Correction of β-thalassemia by CRISPR/Cas9 editing of the α-globin locus in human hematopoietic stem cells

β-thalassemias (β-thal) are a group of blood disorders caused by mutations in the β-globin gene (HBB) cluster. β-globin associates with α-globin to form adult hemoglobin (HbA, α2β2), the main oxygen-carrier in erythrocytes. When β-globin chains are absent or limiting, free α-globins precipitate and damage cell membranes, causing hemolysis and ineffective erythropoiesis. Clinical data show that severity of β-thal correlates with the number of inherited α-globin genes (HBA1 and HBA2), with α-globin gene deletions having a beneficial effect for patients. Here, we describe a novel strategy to treat β-thal based on genome editing of the α-globin locus in human hematopoietic stem/progenitor cells (HSPCs). Using CRISPR/Cas9, we combined 2 therapeutic approaches: (1) α-globin downregulation, by deleting the HBA2 gene to recreate an α-thalassemia trait, and (2) β-globin expression, by targeted integration of a β-globin transgene downstream the HBA2 promoter. First, we optimized the CRISPR/Cas9 strategy and corrected the pathological phenotype in a cellular model of β-thalassemia (human erythroid progenitor cell [HUDEP-2] β0). Then, we edited healthy donor HSPCs and demonstrated that they maintained long-term repopulation capacity and multipotency in xenotransplanted mice. To assess the clinical potential of this approach, we next edited β-thal HSPCs and achieved correction of α/β globin imbalance in HSPC-derived erythroblasts. As a safer option for clinical translation, we performed editing in HSPCs using Cas9 nickase showing precise editing with no InDels. Overall, we described an innovative CRISPR/Cas9 approach to improve α/β globin imbalance in thalassemic HSPCs, paving the way for novel therapeutic strategies for β-thal.

Genetic therapies for the first molecular disease

Sickle cell disease (SCD) is a monogenic disorder characterized by recurrent episodes of severe bone pain, multi-organ failure, and early mortality. Although medical progress over the past several decades has improved clinical outcomes and offered cures for many affected individuals living in high-income countries, most SCD patients still experience substantial morbidity and premature death. Emerging technologies to manipulate somatic cell genomes and insights into the mechanisms of developmental globin gene regulation are generating potentially transformative approaches to cure SCD by autologous hematopoietic stem cell (HSC) transplantation. Key components of current approaches include ethical informed consent, isolation of patient HSCs, in vitro genetic modification of HSCs to correct the SCD mutation or circumvent its damaging effects, and reinfusion of the modified HSCs following myelotoxic bone marrow conditioning. Successful integration of these components into effective therapies requires interdisciplinary collaborations between laboratory researchers, clinical caregivers, and patients. Here we summarize current knowledge and research challenges for each key component, emphasizing that the best approaches have yet to be developed.

Haematological abnormalities in children with sickle cell disease and non-severe malaria infection in western Kenya

Background

In Plasmodium falciparum infection, clinical conditions such as anaemia, thrombocytopenia and leukocytosis are common. Mutation in haemoglobin sub-unit beta gene (HBB) may be a genetic factor responsible for these haematological changes during infection. However, the contributions of the carriage of different HBB genotypes on these changes remain largely unknown.

Methodology

In this cross-sectional study, we evaluated haematological abnormalities in P. falciparum-infected children (n = 217, aged 1–192 months) with different haemoglobin sub-unit beta (HBB) genotypes (HbAA, HbAS and HbSS). Children with acute febrile conditions were recruited at Jaramogi Oginga Odinga Teaching and Referral Hospital at the outpatient clinic. Haematological parameters were determined using Beckman Coulter counter ACTdiff2™ while HBB genotyping was done using TaqMan® SNP genotyping assay. Chi-square (χ²) was used to determine differences between proportions. Differences in haematological parameters were compared across groups using Kruskal Wallis test and between groups using Mann Whitney U test. Partial correlation test was used to determine correlation between haematological parameters and sickle cell genotypes while controlling for age and sex.

Results

Haemoglobin (Hb), [median (IQR); 7.3 (1.3), P = 0.001], haematocrit (HCT), [median (IQR); 26.4 (4.4), P = 0.009], red blood cells (RBC), [median (IQR); 3.2 (1.7), P = 0.048] were markedly reduced in HbSS, however, red cell distribution with (RDW) [median (IQR); 14.9 (3.3), P = 0.030] was increased in malaria infected children with HbSS. Severe anaemia was highest in HbSS (23.1%) followed by HbAA (8.6%) and HbAS (7.1%). There were no differences in platelet count (P = 0.399) hence no severe thrombocytopeania across the genotypes. Leukocytosis was highest in HbSS (69.2%), 42% in HbAS and 31% in HbAA. The RBC, HCT and Hb had negative correlation with RDW in HbSS in malarial-infected children (r = − 0.725, P = 0.008), (r = − 0.718, P = 0.009) and (r = − 0.792, P = 0.002), respectively.

Conclusion

Our study reveals that anaemia is the most common abnormality in malaria-infected children with carriage of HbSS. The RBC, HCT and Hb concentration decrease with increase in RDW levels in infected children with carriage of HbSS compared to other HBB genotypes. Therefore, carriage of HbSS genotype is correlated with severity of haematological abnormalities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06025-7.

Alpha thalassemia, but not βS-globin haplotypes, influence sickle cell anemia clinical outcome in a large, single-center Brazilian cohort

Alpha thalassemia and beta-globin haplotype are considered classical genetic disease modifiers in sickle cell anemia (SCA) causing clinical heterogeneity. Nevertheless, their functional impact on SCA disease emergence and progression remains elusive. To better understand the role of alpha thalassemia and beta-globin haplotype in SCA, we performed a retrospective study evaluating the clinical manifestations of 614 patients. The univariate analysis showed that the presence of alpha-thalassemia -3.7-kb mutation (αα/-α and -α/-α) decreased the risk of stroke development (p = 0.046), priapism (p = 0.033), and cholelithiasis (p = 0.021). Furthermore, the cumulative incidence of stroke (p = 0.023) and cholelithiasis (p = 0.006) was also significantly lower for patients carrying the alpha thalassemia -3.7-kb mutation. No clinical effects were associated with the beta-globin haplotype analysis, which could be explained by the relatively homogeneous haplotype composition in our cohort. Our results reinforce that alpha thalassemia can provide protective functions against hemolysis-related symptoms in SCA. Although, several genetic modifiers can impact the inflammatory state of SCA patients, the alpha thalassemia mutation remains one of the most recurrent genetic aberration and should therefore always be considered first.

Association between haematological parameters and sickle cell genotypes in children with Plasmodium falciparum malaria resident in Kisumu County in Western Kenya

Background

Sickle cell disease (SCD) is a monogenic disorder due to point mutation in the β-globin gene resulting in substitution of Valine for Glutamic acid. The SCD is prevalent in P. falciparum endemic regions such as western Kenya. Carriage of different sickle cell genotypes may influence haematological parameter during malaria. Children resident in malaria holoendemic regions suffer more from malaria-related complications and this is moderated by the presence of the SCD. In the current study, we determined the association between sickle cell genotypes and haematological parameters in children with P. falciparum malaria resident in Kisumu County in Western Kenya.

Methodology

Children (n = 217, aged 1–192 months) with acute febrile condition were recruited at Jaramogi Oginga Odinga Teaching and Referral Hospital. Chi-square (χ2) analysis was used to determine differences between proportions. Differences in haematological parameters were compared across groups using Kruskal Wallis test and between groups using Mann Whitney U test. Multivariate logistic regression analysis controlling for infection status was used to determine the association between sickle cell genotypes and haematological parameters.

Results

Using HbAA as the reference group, multivariate logistic regression analysis revealed that carriage of HbSS was associated with reduced haemoglobin [OR = 0.310, 95% CI = 0.101–0.956, P = 0.041], reduced haematocrit [OR = 0.318, 95% CI = 0.128–0.793, P = 0.014], reduced RBC count [OR = 0.124, 95% CI = 0.045–0.337, P = 0.001], reduced MCHC [OR = 0.325, 95% CI = 0.118–0.892, P = 0.029], increased leucocytosis [OR = 9.283, 95% CI = 3.167–27.210, P = 0.001] and reduced monocytosis [OR = 0.319, 95% CI = 0.123–0.830, P = 0.019]. However, carriage of HbAS was only associated with increased micro-platelets [OR = 3.629, 95% CI = 1.291–8.276, P = 0.012].

Conclusion

Results show that carriage of HbSS in children influence the levels of haemoglobin, haematocrit, RBC, MCHC, WBC and Monocytes. Therefore prior knowledge of HbSS should be considered to improve clinical management of haematological alterations during malaria in children.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-020-05625-z.

Sickle cell disease: A distinction of two most frequent genotypes (HbSS and HbSC)

Sickle cell disease (SCD) consists of a group of hemoglobinopathies in which individuals present highly variable clinical manifestations. Sickle cell anemia (SCA) is the most severe form, while SC hemoglobinopathy (HbSC) is thought to be milder. Thus, we investigated the clinical manifestations and laboratory parameters by comparing each SCD genotype. We designed a cross-sectional study including 126 SCA individuals and 55 HbSC individuals in steady-state. Hematological, biochemical and inflammatory characterization was performed as well as investigation of previous history of clinical events. SCA patients exhibited most prominent anemia, hemolysis, leukocytosis and inflammation, whereas HbSC patients had increased lipid determinations. The main cause of hospitalization was pain crises on both genotypes. Vaso-occlusive events and pain crises were associated with hematological, inflammatory and anemia biomarkers on both groups. Cluster analysis reveals hematological, inflammatory, hemolytic, endothelial dysfunction and anemia biomarkers in HbSC disease as well as SCA. The results found herein corroborate with previous studies suggesting that SCA and HbSC, although may be similar from the genetic point of view, exhibit different clinical manifestations and laboratory alterations which are useful to monitor the clinical course of each genotype.

End points for sickle cell disease clinical trials: patient-reported outcomes, pain, and the brain

To address the global burden of sickle cell disease (SCD) and the need for novel therapies, the American Society of Hematology partnered with the US Food and Drug Administration to engage the work of 7 panels of clinicians, investigators, and patients to develop consensus recommendations for clinical trial end points. The panels conducted their work through literature reviews, assessment of available evidence, and expert judgment focusing on end points related to: patient-reported outcomes (PROs), pain (non-PROs), the brain, end-organ considerations, biomarkers, measurement of cure, and low-resource settings. This article presents the findings and recommendations of the PROs, pain, and brain panels, as well as relevant findings and recommendations from the biomarkers panel. The panels identify end points, where there were supporting data, to use in clinical trials of SCD. In addition, the panels discuss where further research is needed to support the development and validation of additional clinical trial end points.

Polymorphisms in genes that affect the variation of lipid levels in a Brazilian pediatric population with sickle cell disease: rs662799 APOA5 and rs964184 ZPR1

This cross-sectional study investigated associations between SNPs in metabolizing lipid genes, alpha-thalassemia and laboratory parameters in two forms of sickle cell disease (SCD), sickle cell anemia (SCA) and hemoglobin SC disease (HbSC) in a pediatric population. Among the groups SCA and HbSC was found a higher proportion of increased triglycerides (TG) in SCA. High levels of TG were significantly associated with lower hemoglobin (p = 0.006) and HDL-C (p = 0.037), higher white blood cell count (p = 0.027), LDH (p = 0.004) and bilirubins (p < 0.05) in SCD. Patients with HDL-C ≤40 mg/dL had higher markers hemolytic levels. Therapy of HU significantly influenced several hematological and biochemical parameters but not lipid fractions. Genotypes of the APOA5 rs662799 were not associated with lipid levels. The G-risk allele rs964184/ZPRI ZNF259/ZPR1 gene (GC + GG genotypes) was associated with increased levels of TG in children ≥10 years old (p = 0.045) and the atherogenic ratio TG/HDL-C (p = 0.032) in SCD. The use of HU improves levels of hemolysis and inflammation markers in SCD with high TG and, while not interfering with lipid levels, seems to overlap the effect of the G-risk allele in on them. This study reported for the first time that rs964184 SNP could be a genetic modifier of TG in SCD.

Sickle cell disease: a review for the internist

Sickle cell disease (SCD) is the most important hemoglobinopathy worldwide in terms of frequency and social impact, recently recognized as a global public health problem by the World Health Organization. It is a monogenic but multisystem disorder with high morbidity and mortality. Vaso-occlusion, hemolytic anemia and vasculopathy are the hallmarks of SCD pathophysiology. This review focuses both on "time-dependent" acute clinical manifestations of SCD and chronic complications commonly described in adults with SCD. The review covers a broad spectrum of topics concerning current management of SCD targeted at the internists and emergency specialists who are increasingly involved in the care of acute and chronic complications of SCD patients.

Genetic variation influencing hemoglobin levels and risk for anemia across populations

Hemoglobin (Hb) concentration is the outcome of the interaction between genetic variation and environmental factors, including nutritional status, sex, age, and altitude. Genetic diversity influencing this protein is complex and varies widely across populations. Variants related to abnormal Hb or altered characteristics of the erythrocytes increase the risk for anemia. The most prevalent are related to the inherited globin abnormalities affecting Hb production and structure. Malaria-endemic regions harbor the highest frequencies of variants associated with the most frequent monogenic diseases and the risk for nonnutritional anemia and are considered as public health problems. Variation in genes encoding for enzymes and membrane proteins in red blood cells also influence erythrocyte life span and risk for anemia. Most of these variants are rare. Interindividual variability of hematological parameters is also influenced by common genetic variation across the whole genome. Some of the identified variants are associated with Hb production, erythropoiesis, and iron metabolism. Specialized databases have been developed to organize and update the large body of available information on genetic variation related to Hb variation, their frequency, geographical distribution, and clinical significance. Our present review analyzed the underlying genetic factors that affect Hb concentrations, their clinical relevance, and geographical distribution across populations.

The past, present and future management of sickle cell retinopathy within an African context

Sickle cell retinopathy is a potentially blinding condition that affects young people in the working age group. This review looks at the past, present and future management of sickle cell retinopathy within an African context. After Sickle cell disease was first reported in 1910, some reports from Africa were pivotal in describing the retinal changes associated with the disease. It soon became obvious that there was a varied clinical picture and clinical course. Several landmark studies were carried out in Jamaica to help elucidate the complexities of the disease and outline appropriate clinical management. In most of the developed world, the clinical management of sickle cell disease has improved with concurrent improvement in outcomes. Currently resource constraints in most Sub-Saharan African countries where there is a high burden of disease means that the management of sickle cell retinopathy is fraught with numerous challenges. Future large scale trials in Africa shall hopefully help to better elucidate the mechanisms behind proliferative sickle retinopathy and help in the development of new and improved therapeutic pathways. The use of technology can help immensely in the screening of patients with sickle cell to detect early proliferative changes and if necessary treat accordingly.

Differences in prenatal aneuploidy screening among African-American women with hemoglobin S variants

OBJECTIVE

It has been shown that hemoglobinopathies increase the risk of pregnancy complications and placental dysfunction. This could alter the placental analytes examined during prenatal aneuploidy screening. Our objective was to determine whether there is a difference in maternal serum screening results for women with hemoglobin S variants (AS, SS, SC, S/beta thalassemia) compared with women with normal hemoglobin (AA).

STUDY DESIGN

This is a retrospective cohort study in African-American women receiving aneuploidy screening at MedStar Washington Hospital Center from 2008 to 2015. We evaluated 79 women with hemoglobin S variants (69 AS and 10 sickle cell disease (SCD)) and 79 controls. Descriptive statistics (means, medians, and frequencies) were calculated for each group. For the continuous variables, differences in the averages between the two groups were tested using the t test or Wilcoxon rank sum test. Differences in the averages between three or more groups were tested using the analysis of variance test or the Kruskal-Wallis test.

RESULTS

Demographics were similar between cases and controls. The overall screen positive rate for Down syndrome among patients with sickle cell trait (AS) was 3% (2/69). For patients with SCD, the overall screen positive rate was 10% (1/10). None of the women in the control population (AA) has a positive Down syndrome screening result (0/79).

CONCLUSION

As expected, the screen positive rate in patients with hemoglobin S variants was higher than controls, however, patients with sickle cell trait do not appear to be at an increased risk for false-positive results with serum aneuploidy screening compared with the general population. We did, however, find an increased risk of false-positive quad screen results in patients with sickle cell disease.

Genetic modifiers of severity in sickle cell disease

Sickle cell disease (SCD) is one of the most common single disease disorders world-wide. It is remarkable for its clinical heterogeneity, even among individuals with identical genotypes. Some individuals experience morbidity and mortality in early childhood, while others have a relatively mild course, and normal or near normal life expectancy. Many clinical complications are associated with SCD; most notably frequent pain episodes, stroke, acute chest syndrome, avascular necrosis, nephropathy, retinopathy and pulmonary hypertension. While the effects of higher fetal hemoglobin (HbF) levels, UGTA1A polymorphisms, alpha-thalassemia and G6PD deficiency on SCD has been extensively studied, these variables do not explain all of the clinical heterogeneity of SCD. It is not known why some patients develop certain complications, and it is difficult to predict which complications a particular patient will experience. Much work has been done to identify genetic variants associated with these disease complications; many associations remain unvalidated. As the field continues to move beyond small sample collections and candidate gene approaches into whole genome sequencing and merging of samples from all over the world, we will identify more genetic variants associated with development of specific SCD related complications, and hopefully leverage this knowledge into targeted therapies.

Common α-globin variants modify hematologic and other clinical phenotypes in sickle cell trait and disease

Co-inheritance of α-thalassemia has a significant protective effect on the severity of complications of sickle cell disease (SCD), including stroke. However, little information exists on the association and interactions for the common African ancestral α-thalassemia mutation (-α3.7 deletion) and β-globin traits (HbS trait [SCT] and HbC trait) on important clinical phenotypes such as red blood cell parameters, anemia, and chronic kidney disease (CKD). In a community-based cohort of 2,916 African Americans from the Jackson Heart Study, we confirmed the expected associations between SCT, HbC trait, and the -α3.7 deletion with lower mean corpuscular volume/mean corpuscular hemoglobin and higher red blood cell count and red cell distribution width. In addition to the recently recognized association of SCT with lower estimated glomerular filtration rate and glycated hemoglobin (HbA1c), we observed a novel association of the -α3.7 deletion with higher HbA1c levels. Co-inheritance of each additional copy of the -α3.7 deletion significantly lowered the risk of anemia and chronic kidney disease among individuals with SCT (P-interaction = 0.031 and 0.019, respectively). Furthermore, co-inheritance of a novel α-globin regulatory variant was associated with normalization of red cell parameters in individuals with the -α3.7 deletion and significantly negated the protective effect of α-thalassemia on stroke in 1,139 patients with sickle cell anemia from the Cooperative Study of Sickle Cell Disease (CSSCD) (P-interaction = 0.0049). Functional assays determined that rs11865131, located in the major alpha-globin enhancer MCS-R2, was the most likely causal variant. These findings suggest that common α- and β-globin variants interact to influence hematologic and clinical phenotypes in African Americans, with potential implications for risk-stratification and counseling of individuals with SCD and SCT.