MRSA pyomyositis complicating sickle cell anaemia.

A patient being treated for sickle cell crisis developed swollen, painful, indurated, discoloured thighs after several days in hospital. Imaging revealed the presence of multiple small abscesses in the muscle and methicillin resistant Staphylococcus aureus (MRSA) was cultured from aspirated fluid. Pyomyositis usually occurs in association with damaged muscle and impaired host defences. Staphylococcus is the most frequent organism involved. It is not a common complication of sickle cell disease, although it may be under diagnosed. Availability of advanced imaging techniques facilitates early diagnosis of pyomyositis.     

Hb F Levels in Indian Sickle Cell Patients and Association with the HBB Locus Variant rs10128556 (C>T), and the HBG XmnI (Arab-Indian) Variant

The prevalence of sickle cell disease in India is very high. Hb F is one of the most powerful modulators of disease severity in sickle cell disease patients. It was traditionally thought that the disease is milder in Indian sickle cell disease patients predominantly due to the Arab-Indian haplotype characterized by the HBG XmnI [rs7482144 (G>A)] variant, which is associated with increased Hb F levels. In the current study, we investigated the Hb F levels in individuals with the rs10128556 (C>T) variant and also determined its linkage with the HBG XmnI variant. The present study was conducted on a cohort of 275 individuals, which consisted of 221 patients with sickle cell disease and 54 patients with sickle cell trait. Analysis of hemoglobin (Hb) fractions and variants was done on the high performance liquid chromatography (HPLC) system. Genotyping for rs10128556 was done by direct sequencing of the products. Mean Hb F levels in the sickle cell disease patients was 19.36?±?6.79. The genotypic frequencies for rs10128556 were 82.0% (TT), 16.7% (CT) and 1.3% (CC) for sickle cell disease patients. The minor C allele resulted in 52.0% decrease in Hb F levels when homozygous and 7.0% decrease when heterozygous. The rs10128556 single nucleotide polymorphism (SNP) was in strong but not complete linkage with the HBG XmnI variant. In conclusion, the study determined for the first time the frequency and association of rs10128556 in Indian sickle cell disease patients with Hb F. It also established that it was not in complete linkage with the HBG XmnI variant in this high risk population.     

The release of nitric oxide and superoxide anion by neutrophils and mononuclear cells from patients with sickle cell anaemia

The aim of this work was to investigate the release of nitric oxide and superoxide by neutrophils and mononuclear cells from patients with sickle cell anaemia. Nitric oxide release was assayed by the ability of leucocytes to inhibit thrombin-induced washed platelet aggregation. Superoxide release was assessed by a cytochrome c reduction assay. Neutrophils from sickle cell anaemia patients released nitric oxide in a similar manner to those from healthy controls, because inhibition of platelet aggregation by neutrophils from sickle cell anaemia or from healthy controls was blocked by the inhibitor of nitric oxide synthesis N ^ω-nitro-l -arginine methyl ester (300 μm ), but not by N ^ω-nitro-d -arginine methyl ester (300 μm ) and was reversed by l -arginine (1 mm ). Additionally, a similar number of neutrophils from sickle cell anaemia patients and from healthy controls was required to inhibit platelet aggregation. Mononuclear cells from sickle cell anaemia patients inhibited platelet aggregation only in the presence of superoxide dismutase (60 U ml^?1). Phorbol 12-myristate 13-acetate (PMA, 30 nm )- or zymosan (100 particles/cell)-induced release of superoxide by mononuclear cells from sickle cell anaemia patients was significantly higher than that observed in mononuclear cells from healthy controls (P < 0.001 and P < 0.01 respectively, Mann-Whitney test). The levels of superoxide released by neutrophils from sickle cell anaemia patients were similar to those from healthy controls. We conclude that mononuclear cells from sickle cell anaemia patients release more superoxide than those from healthy controls, when stimulated with PMA or zymosan in vitro. Considering that superoxide inactivates nitric oxide, that nitric oxide is an important endogenous vasodilator, and that superoxide produces oxidant damage, this greater production of superoxide by mononuclear cells from sickle cell anaemia patients may represent an additional risk factor for the obstruction of the microcirculation and tissue damage in these patients.     

Prevalence of Sickle Cell Disease in a Pediatric Population Suffering From Severe Infections: A Congolese Experience

Neonatal screening for sickle cell anemia is not a common practice in the Democratic Republic of Congo (DRC). Children with sickle cell disease are known to have an increased risk of infections. We conducted a pilot study to determine the prevalence of sickle cell anemia during episodes of severe infection. A prospective study was conducted from July 2009 to July 2011. The study sites included four public hospitals at Kinshasa, DRC. The study population was selected from the source population using three-stage sampling. A total of 247 children with severe infection were consecutively recruited and screened for sickle cell disease. There were 124 boys (50.2%) and 123 girls (49.8%) with a sex-ratio of 1:1. More than two-thirds of patients (66.0%) were children between 1 and 24 months of age. Among these 247 children, 19 (7.7%) were homozygous sickle cell anemia patients (Hb SS). No patient had received Hemophilus influenzae, streptococcus pneumoniae and salmonella sp vaccines. Sepsis was the most common form of severe infection observed in 44.5% of patients. A total of 19 (7.7%) positive blood cultures were recorded. Most cases were reported in sickle cell patients (15.8%) compared to 6.1% in children who were negative for Hb S [β6(A3)Glu→Val; HBB: c.20A>T] (p?>?0.05). Of 247 children with severe infection, approximately 8.0% carried unknown sickle cell anemia mutations. Based on the findings in this study, opportunistic testing for sickle cell anemia is possible and worthwhile in children who present with severe infection in DRC until neonatal screening is universal.     

Association of the CCR5Δ32 Mutant Genotype with Sickle Cell Disease in Egyptian Patients

Abstract

Sickle cell disease is considered the most common single base mutation in the world, with >250,000 new patients being discovered each year. It consists of a wide spectrum of clinical presentations and complications. The CCR5Δ32 is the mutant genotype of C–C chemokine receptor 5 (CCR5). It is widely distributed due to several micro organisms that target macrophages in different populations. Theoretically, CCR5Δ32 confers an advantage to sickle cell disease patients. The chronic inflammatory response is the main pathogenesis in sickle cell disease, thus, the presence of the null CCR5Δ32 mutant genotype prevents the Th1-type immune response caused by the CCR5 chemokine receptor. This study aimed to define the true incidence of the CCR5Δ32 mutant genotype and to correlate its presence with the clinical and/or the radiological findings in sickle cell disease patients. We proposed decreased morbidity and prolonged survival of sickle cell disease patients carrying the CCR5Δ32 genotype. The study showed relatively the same prevalence (5.1%) of the CCR5Δ32 mutant genotype found in 500 sickle cell disease patients when compared to 1000 healthy controls (5.0%) with the same ethnic background. Despite the near prevalence of the incidence to controls, we suggest that CCR5Δ32 is relatively beneficial to sickle cell disease patients as polymorphic patients showed uncomplicated clinical presentation in contrast to other patients without the CCR5Δ32.     

Incidence and Predictors of Bacterial infection in Febrile Children with Sickle Cell Disease

Abstract

Children with sickle cell disease are at increased risk of developing bacteremia and other serious bacterial infections. Fever is a common symptom in sickle cell disease and can also occur with sickle cell crises and viral infections. We aimed to evaluate the incidence and predictors of bacteremia and bacterial infection in children with sickle cell disease presenting with fever to a district hospital and sickle cell center in London. A retrospective analysis was performed on all attendances of children (aged under 16 years) with sickle cell disease presenting with a fever of 38.5?°C or higher over a 1-year period. Confirmed bacterial infection was defined as bacteremia, bacterial meningitis, urinary tract infection (UTI), pneumonia, osteomyelitis or other bacterial infection with positive identification of organism. Children were defined as having a suspected bacterial infection if a bacterial infection was suspected clinically, but no organism was identified. Over a 1-year period there were 88 episodes analyzed in 59 children. Bacteremia occurred in 3.4% of episodes and confirmed bacterial infection in 7.0%. Suspected bacterial infection occurred in 33.0%. One death occurred from Salmonella typhirium septicemia. C-reactive protein (CRP) level and white blood cell (WBC) count were both significantly associated with bacterial infection (p?=?0.004 and 0.02, respectively.) In conclusion, bacterial infections continue to be a significant problem in children with sickle cell disease. C-reactive protein was significantly associated with bacterial infections, and could be included in clinical risk criteria for febrile children with sickle cell disease.     

Use of Direct Oral Anticoagulants in Patients with Sickle Cell Disease and Venous Thromboembolism: A Prospective Cohort Study of 12 Patients

Abstract

Patients with sickle cell disease have an increased risk of venous thromboembolism (VTE) and with a mortality 2-fold higher. The anticoagulation of VTE in a young population is an important question. Indeed, hemorrhagic complications of anticoagulation may occur more frequently than in the general population. The use of a direct oral anticoagulant (DOAC) is not recommended for VTE in patients with sickle cell disease because those patients were not included in the clinical studies. We aimed to study the safety of using DOACs in a prospective cohort of patients with sickle cell disease and VTE. We prospectively followed the cohort of all sickle cell disease patients undergoing recent DOAC treatment for VTE at a sickle cell disease reference center. Twelve patients received rivaroxaban for VTE (eight women and four men). The median age was 27?years (20–45). The sickle cell disease variants included homozygous Hb SS (HBB: c.20A>T) in eight patients, Hb S-β⁺-thalassemia (Hb S-β⁺-thal) in two, Hb S-β⁰-thal in one and Hb S-Hb C (HBB: c.19G>A) in one. The cumulative duration of follow-up was 3134?days under rivaroxaban treatment. There were two thrombotic events, including a patient with a double positivity of antiphospholipid antibodies. No major bleeding was observed, and 6/12 patients presented minor bleeding (epistaxis: n?=?4; anal fissure bleeding: n?=?1; menorrhagia n?=?4). Of these, 3/6 required their treatment to be switched to apixaban, which stopped the bleeding. Direct oral anticoagulants may be an alternative treatment for VTE in patients with sickle cell disease, except for an associated antiphospholipid syndrome.     

Effects of oxidative stress on red blood cell rheology in sickle cell patients

Sickle cell anaemia (SS) and sickle cell‐haemoglobin C disease (SC) patients exhibit severe red blood cell (RBC) rheological alterations involved in the development of several complications. The contribution of oxidative stress in these haemorheological abnormalities is still unknown. We compared RBC reactive oxygen species (ROS) and glutathione (GSH) content, and the haemorheological profile of SS (n = 11), SC (n = 11) and healthy subjects (n = 12) at baseline and after in‐vitro treatment with t‐butyl hydroperoxide (TBHP). We showed: (i) higher RBC ROS content in SS and SC patients, with the highest level observed in SS patients; (ii) lower RBC GSH content in sickle syndrome patients, especially in SS patients; (iii) TBHP increased RBC ROS production and decreased RBC GSH content in all groups; (iv) TBHP decreased RBC aggregation and increased the strength of RBC aggregates in all groups but the increase in RBC aggregates strength was greater in sickle cell patients; (v) TBHP decreased RBC deformability in the three groups but with a higher magnitude in sickle cell patients. These data suggest that RBCs from sickle cell patients have an exaggerated response to oxidative stress, which is accompanied by a profound abnormal haemorheological profile, with greater alterations in SS than in SC patients.     

Phenotypic Diversity of Sickle Cell Disease in Patients with a Double Heterozygosity for Hb S and Hb D-Punjab

Phenotypic heterogeneity for sickle cell disease is associated to several genetic factors such as genotype for sickle cell disease, β-globin gene cluster haplotypes and Hb F levels. The coinheritance of Hb S (HBB: c.20A?>?T) and Hb D-Punjab (HBB: c.364G?>?C) results in a double heterozygosity, which constitutes one of the genotypic causes of sickle cell disease. This study aimed to assess the phenotypic diversity of sickle cell disease presented by carriers of the Hb S/Hb D-Punjab genotype and the Bantu [–?+?– – – –] haplotype. We evaluated medical records from 12 patients with sickle cell disease whose Hb S/Hb D-Punjab genotype and Bantu haplotype were confirmed by molecular analysis. Hb S and Hb D-Punjab levels were quantified by chromatographic analysis. Mean concentrations of Hb S and Hb D-Punjab were 44.8?±?2.3% and 43.3?±?1.8%, respectively. Painful crises were present in eight (66.7%) patients evaluated, representing the most common clinical event. Acute chest syndrome (ACS) was the second most prevalent manifestation, occurring in two individuals (16.7%). Three patients were asymptomatic, while another two exhibited greater diversity of severe clinical manifestations. Medical records here analyzed reported a significant clinical diversity in sickle cell disease ranging from the absence of symptoms to wide phenotypic variety. The sickle cell disease genotype, Bantu haplotype and hemoglobin (Hb) levels did not influence the clinical diversity. Thus, we concluded that the phenotypic variation in sickle cell disease was present within a specific genotype for disease regardless of the β-globin gene cluster haplotypes.     

New developments in anti‐sickling agents: can drugs directly prevent the polymerization of sickle haemoglobin in vivo?

The hallmark of sickle cell disease is the polymerization of sickle haemoglobin due to a point mutation in the β‐globin gene (HBB). Under low oxygen saturation, sickle haemoglobin assumes the tense (T‐state) deoxygenated conformation that can form polymers, leading to rigid erythrocytes with impaired blood vessel transit, compounded or initiated by adhesion of erythrocytes to endothelium, neutrophils and platelets. This process results in vessel occlusion and ischaemia, with consequent acute pain, chronic organ damage, morbidity and mortality. Pharmacological agents that stabilize the higher oxygen affinity relaxed state (R‐state) and/or destabilize the lower oxygen affinity T‐state of haemoglobin have the potential to delay the sickling of circulating red cells by slowing polymerization kinetics. Relevant classes of agents include aromatic aldehydes, thiol derivatives, isothiocyanates and acyl salicylates derivatives. The aromatic aldehyde, 5‐hydroxymethylfurfural (5‐HMF) increases oxygen affinity of sickle haemoglobin and reduces hypoxia‐induced sickling in vitro and protects sickle cell mice from effects of hypoxia. It has completed pre‐clinical testing and has entered clinical trials as treatment for sickle cell disease. A related molecule, GBT440, has shown R‐state stabilization and increased oxygen affinity in preclinical testing. Allosteric modifiers of haemoglobin as direct anti‐sickling agents target the fundamental pathophysiological mechanism of sickle cell disease.     

Calpromotin,a cytoplasmic protein,is associated with the formation of dense cells in sickle cell anemia

We have tested the hypothesis that dense cell formation in sickle cell disease is associated with increased binding of calpromotin to the membrane, an event that occurs during the activation of calcium-dependent potassium transport. By SDS polyacrylamide gel electrophoresis, we found that sickle cell membranes contained more calpromotin than did normal membranes when stained with Coomassie brilliant blue or when transferred to nitrocellulose paper and immunostained with horseradish peroxidase. Also, the membranes from dense sickle cells contained significantly (P = 0.00055) higher levels of calpromotin, 2.62 ± 1.59 μg/mg membrane protein, compared to light sickle cells, 1.40 ± 0.70 μg/mg membrane protein, when measured by an enzyme-linked immunosorbent assay. The ratio of calpromotin associated with dense cell membranes to light cell membranes was significantly greater than 1.0 (P < 0.00005). Transmission electron micrographs of immunogold-labelled membranes supported the increase in calpromotin binding in dense sickle cell membranes. In addition, the immunogold probe demonstrated clustering, which was not observed in light sickle cell membranes nor in normal membranes. Finally, we incubated HbSS cells in vitro using a repetitive deoxygenation/reoxygenation procedure to produce dense cells and then measured the levels of calpromotin associated with their membranes. As expected, the levels of calpromotin bound to the membrane doubled during the procedure relative to the basal levels at the beginning of the incubation. The correlation coefficient, calculated between the increase in dense cell formation and the increase in calpromotin associated with the membrane, was statistically significant (P = 0.038). The results demonstrate that an increase in calpromotin binding to the membrane is associated with dense cell formation presumably through the activation of the calcium-dependent potassium channel. Am. J. Hematol. 56:100–106, 1997. © 1997 Wiley-Liss, Inc.     

Myonecrosis and myofibrosis as complications of sickle cell anemia

Painful crises in sickle cell anemia are associated with infarction and subsequent fibrosis of many different organs. Myonecrosis secondary to muscle infarction during a crisis and subsequent fibrosis are often not recognized as complications of sickle cell anemia. We describe four patients, all of whom had recurrent episodes of symmetric proximal muscle pain and swelling as prominent features of their crises. Muscle biopsies showed acute myonecrosis with a minimal inflammatory reaction as well as myofibrosis with abundant collagen deposition. Chronic sequelae consisted of muscle induration, atrophy, and contractures.     

Endothelial Function in Patients with Sickle Cell Anemia During and After Sickle Cell Crises

Background:Prior studies have demonstrated increased adherence of sickle cell erythrocytes to vascular endothelial cells. While decreased production of nitric oxide and increased production of adhesion molecules have been implicated in this pathophysiology, the relative contribution of these mechanisms during acute sickle cell crises as compared to steady state conditions have not been elucidated.Methods and results: We studied 10 consecutive young adult patients presenting with a sickle cell crisis. Endothelial function was evaluated by a non-invasive brachial artery shear stress method. Serum levels of adhesion molecules were obtained during the crisis. Both brachial artery responsiveness and serum levels of adhesion molecules were then repeated at steady state. Ten age and gender matched volunteers served as a control group. Impaired endothelial function and impaired endothelium-independent vasodilatation were observed in all sickle cell patients during both steady state and during crisis. Flow mediated dilation (FMD)% was 3.25 ± 2.76% during crisis, 4.57 ± 4.11 at steady state, compared with the control group FMD of 11.64 ± 7.69% (p < 0.001). Flow independent dilation was 10.35 ± 11.3% during crisis, 10.03 ± 6.52% at steady state, compared with control group FID of 24.17 ± 11.87% (p < 0.001). Levels of cell adhesion molecules and markers of inflammation were increased in sickle cell crisis patients compared with the control group: sCD40 ligand levels during the acute crisis were over twice the level of normal matched volunteers (p = 0.02), and similarly significant increases were seen for E-selectin (p = 0.008), ICAM-1 (p = 0.037) and VCAM-1 levels (p = 0.01). The levels of each of these biomarkers was not significantly increased during acute crises as compared to patients’ recovery state.Conclusions: Sickle cell anemia patients have severe systemic endothelial dysfunction as demonstrated by both brachial artery assessment and increased serum levels of adhesion molecules. These abnormalities characterize not only the sickle cell crisis but also the steady state pathophysiology of sickle cell anemia.     

The Assessment and Sustainable Management of Sickle Cell Disease in the Indigenous Tharu Population of Nepal

Sickle cell disease is an inherited hemoglobinopathy associated with significant morbidity and mortality. Reports suggest a high sickle cell disease burden among the indigenous Tharu population of Nepal, who for centuries have inhabited regions where malaria is endemic. Unfortunately, health care resources are limited and often inaccessible for Tharu individuals suffering from sickle cell disease. We conducted a large-scale screening effort to estimate the prevalence of Hb S (HBB: c.20A>T) among the Tharu population and delivered community-based education sessions to increase sickle cell disease awareness. A total of 2899 Tharu individuals aged 6 months to 40 years in the rural district of Dang in Western Nepal were screened using a sickling test, of whom, 271 [9.3%; 95% confidence interval (95% CI): 8.3–10.4%] screened positive for Hb S. Those who screened positive were offered diagnostic gel electrophoresis testing. Of the 133 individuals who underwent diagnostic testing, 75.9% (n?=?101) were confirmed to be Hb AS heterozygotes, 4.5% (n?=?6) were confirmed to be Hb SS homozygotes and 19.5% (n?=?26) were false positives. These findings support a large burden of sickle cell disease among the Tharu population and highlight the importance of appropriate resource allocation and management. With a positive predictive value of 80.0% (95% CI: 73.0-87.0%), the sickling test in conjunction with raising local sickle cell disease awareness may be a simple and sustainable way to promote access to health resources.     

Experience with the Port-A-Cath in sickle cell disease

Peripheral vein access is often a problem in patients with sickle cell disease (SCD). Totally implantable venous access devices (TIVAD) have offered other groups of patients safe long-term venous access. We reviewed our own experience with the use of a Port-A-Cath device in five patients with SCD undergoing exchange transfusion programmes. All five lines required removal due to infection associated with SBE, septic arthritis, pulmonary embolus and axillary vein thrombosis. The organisms involved were Staphylococcus aureus (3), Staphylococcus epidermidis (1) and Streptococcus sp. (1). The median working life of the catheters was 240 days (range 61–428). The median length of time from presentation to the diagnosis of a line-associated infection was 29 days (range 1–58). The rate of complications (0.4 per 100 patient days) in this small group of patients contrasts with the lower rates in patients with HIV and malignancy (0–0.1 per 100 patient days). Our results suggest that patients with SCD suffer an unacceptable incidence of infective complications associated with the Port-A-Cath. Bone infection is more common where there is pre-existing infarcted tissue. While these systems provide a valuable tool, our experience has led us to discontinue the use of TIVADs in SCD.     

Mitral valve prolapse in sickle cell disease. Presumptive evidence for a linked connective tissue disorder

To determine the prevalence of mitral valve prolapse in sickle cell disease, M-mode echocardiography was performed on 57 patients with sickle cell disease and 35 patients with chronic anemia of end-stage renal disease (anemic control group). In 25% (14/57) of patients with sickle cell disease, unequivocal mitral valve prolapse was diagnosed by echocardiography; all these patients had a mobile systolic click and/or late systolic murmur. This figure was significantly greater than the reported 5% to 6% prevalence in the general adult population, the 1% to 3% prevalence in the black population, and the 3.0% prevalence (1/35) in the anemic control group. The association of mitral valve prolapse and sickle cell disease cannot be explained on the basis of left ventricular size, systolic function, ischemic left ventricular or papillary muscle dysfunction, or chronic anemia. Therefore, a linked connective tissue defect in these two diseases is a hypothesis worthy of further investigation.     

Parent education and biologic factors influence on cognition in sickle cell anemia

Children with sickle cell anemia have a high prevalence of silent cerebral infarcts (SCIs) that are associated with decreased full‐scale intelligence quotient (FSIQ). While the educational attainment of parents is a known strong predictor of the cognitive development of children in general, the role of parental education in sickle cell anemia along with other factors that adversely affect cognitive function (anemia, cerebral infarcts) is not known. We tested the hypothesis that both the presence of SCI and parental education would impact FSIQ in children with sickle cell anemia. A multicenter, cross‐sectional study was conducted in 19 US sites of the Silent Infarct Transfusion Trial among children with sickle cell anemia, age 5–15 years. All were screened for SCIs. Participants with and without SCI were administered the Wechsler Abbreviated Scale of Intelligence. A total of 150 participants (107 with and 43 without SCIs) were included in the analysis. In a multivariable linear regression model for FSIQ, the absence of college education for the head of household was associated with a decrease of 6.2 points (P = 0.005); presence of SCI with a 5.2 point decrease (P = 0.017); each $1000 of family income per capita with a 0.33 point increase (P = 0.023); each increase of 1 year in age with a 0.96 point decrease (P = 0.023); and each 1% (absolute) decrease in hemoglobin oxygen saturation with 0.75 point decrease (P = 0.030). In conclusion, FSIQ in children with sickle cell anemia is best accounted for by a multivariate model that includes both biologic and socioenvironmental factors. Am. J. Hematol. 89:162–167, 2014. © 2013 Wiley Periodicals, Inc.     

High oxygen environment during pregnancy rescues sickle cell anemia mice from prenatal death

Several mouse models of sickle cell disease have been developed for the study of the pathophysiology of sickle cell disease and the investigation of drug and gene therapies. In previous years, we produced a sickle cell anemia mouse model in which the endogenous mouse α- and β-globin genes were knocked out and replaced by the human α- and β^s-globin transgenes. The β^s-globin gene was contained in a 240 kb YAC that preserved the entire native genomic context of the β-globin locus. These mice have hemolytic anemia, reticulocytosis and irreversible sickle cells in the peripheral blood, as well as other pathological features of sickle cell disease. However, in the embryo, the γ-globin, like the mouse embryonic globin, declined quickly, and was replaced by β^s-globin expression from 12 days of gestation. The low level of fetal hemoglobin expression in utero led to intrauterine sickling and fetal death so that very few live-born sickle cell anemia mice could be obtained. To rescue these mice from intrauterine death, we investigated the effect of placing the pregnant mothers in a high O₂ environment. From the tenth day of gestation onwards, we placed the mothers into a chamber containing 50% O₂ and kept them with the newborn pups in it for another 10 days after birth. The frequency of sickle cell anemia mice we obtained was increased from less than 2% to 35%. The survived sickle cell anemia mice develop congestion, atrophy, and infarcts in multiple organs similar to those found in patients with sickle cell disease. We conclude that a high oxygen environment can be used to obtain more sickle cell anemia mice in those models that have a high perinatal mortality. The higher yield of these mice has facilitated physiological and therapeutic studies of sickle cell anemia.     

Determinants of resting cerebral blood flow in sickle cell disease

Stroke is common in children with sickle cell disease and results from an imbalance in oxygen supply and demand. Cerebral blood flow (CBF) is increased in patients with sickle cell disease to compensate for their anemia, but adequacy of their oxygen delivery has not been systematically demonstrated. This study examined the physiological determinants of CBF in 37 patients with sickle cell disease, 38 ethnicity matched control subjects and 16 patients with anemia of non‐sickle origin. Cerebral blood flow was measured using phase contrast MRI of the carotid and vertebral arteries. CBF increased inversely to oxygen content (r² = 0.69, P < 0.0001). Brain oxygen delivery, the product of CBF and oxygen content, was normal in all groups. Brain composition, specifically the relative amounts of grey and white matter, was the next strongest CBF predictor, presumably by influencing cerebral metabolic rate. Grey matter/white matter ratio and CBF declined monotonically until the age of 25 in all subjects, consistent with known maturational changes in brain composition. Further CBF reductions were observed with age in subjects older than 35 years of age, likely reflecting microvascular aging. On multivariate regression, CBF was independent of disease state, hemoglobin S, hemoglobin F, reticulocyte count and cell free hemoglobin, suggesting that it is regulated similarly in patients and control subjects. In conclusion, sickle cell disease patients had sufficient oxygen delivery at rest, but accomplish this only by marked increases in their resting CBF, potentially limiting their ability to further augment flow in response to stress. Am. J. Hematol. 91:912–917, 2016. © 2016 Wiley Periodicals, Inc.     

Unusual β-Globin Haplotype Distribution in Newborns from Bengo,Angola

Abstract

Mutations on the HBB gene are a common cause of hemoglobinopathies, including sickle cell anemia, a severe genetic condition that constitutes a major public health concern. The aim of this study was to determine the prevalence of sickle cell anemia and β-globin haplotype distribution in newborns from the Bengo region. The first two exons of β-globin gene were sequenced, and the variability at the single nucleotide polymorphism (SNP) defining the Hb S (HBB: c.20A>T) haplotypes, was analyzed by a SNaPshot^® Multiplex system. About 3.3% of the children were homozygous for Hb S, and 82.2% had as background the Bantu/Central African Republic (BAN/CAR) haplotype, 11.2% the Benin (BEN) and 6.6% the Senegal (SEN). The estimate of Hb S reached the very high value of 0.1476?±?0.0133, with the aggravating factor of 82.2% of the sickle alleles being anchored in the BAN/CAR haplotype, associated with the more severe sickle cell anemia phenotypes. Also, the high prevalence of the SEN haplotype was not expected, having therapeutic consequences since is associated with more severe outcomes. In addition, two β-thalassemia (β-thal) variants were also detected, IVS I-110 (G>A) (HBB: c.93-21G>A) and codon 39 (C>T) (HBB: c.118C>T), together totaling a frequency of 1.3%. Some of the newborns with these mutations were compound heterozygotes for Hb S, likely carrying genotypes consistent with sickle cell disease. As a whole, infants molecularly diagnosed with sickle cell disease accounted for 4.5% of newborns from Bengo, Angola, a figure that per se, highlights the urgent need of implementing policies warranting surveillance of these children, in parallel with community education in the region.