Sickle Disorders Research Articles

Epidemiology and etiology of pediatric stroke

Stroke may be an underestimated disease in children and adolescents. Several studies report an annual incidence as high as for brain tumors: 2-13 children for arterial ischemic, 1-5 for hemorrhagic stroke and 0.67/100,000 children for cerebral venous thrombosis. Recurrence of stroke ranges from 10-20% and depends on the underlying risk factors. Genetic predisposition underlying diseases and risk factors can often not be separated very precisely. The most prominent risk factors are vasculapathies and congenital heart disease, sickle cell anemia, coagulopathies, metabolic disorders and infections. Disorders in lipometabolism and genetic predisposition are now known to play also a role in the pathogenesis of pediatric stroke. A distinct stroke etiology can be determined only in a minority of children. However, most of them (> 80%) have more than one risk factor. The purpose of this review is to describe the epidemiology, risk factors, and etiologies of pediatric stroke in order to give rationales for understanding clinical symptoms and treatment decisions.

Spinal Artery Thrombosis: An Unrecognized Severe Complication in Thalassemia and Sickle Disorders

AbstractAbstract 1155 Introduction.Anterior spinal artery thrombosis (AST) results in sudden, often irreversible sensory and motor loss, with partial or complete paraplegia. This is recognized as a complication of: prothrombotic states; right to left shunting; trauma and spinal surgery. Both venous and arterial thrombosis, including the central nervous system, are well-recognized risks in sickle cell disease (SCD) but AST has not been described. In thalassemia disorders (Thal), cerebral infarction, often silent, is increasingly recognized (Mussalam et al, Thromb Res, Aug 2012). However AST is not a recognized complication. Here we describe four cases of acute onset AST in adults (3 Thal major, 1 SCD), leading to severe neurological irreversible or partially reversible deficits. Patients and Methods.Patients described were attending outpatients for monitoring drawn from two large adults clinics in the UK (UCLH, Whittington, over 1500 hemoglobinopathy patients) and Italy (Ospedale Maggiore Policlinico, Milan, 400 patients). All events occurred within a 3 year period. Results.Presenting symptoms and Magnetic Resonance Imaging (MRI) findings are shown in the Table. All cases presented acutely with a sensory level on examination and with bladder dysfunction. Three presented with motor weakness of both lower limbs (1 case initially in one limb). Case 3 presented with a sensory deficit affecting the sacral region but no motor deficit. Partial reversibility occurred in cases 1 and 3. In Thal cases, no prodromal syndrome and no prior history of thrombosis were seen. MRI showed changes consistent with acute cord ischemia (delayed in case 4 until 5 days). Extra-medullary hematopoiesis was demonstrated by MRI only in case 2, but was not sufficient to cause cord compression. Cerebrospinal fluid analysis was normal in all cases. Concomitant risk factors such as autoimmune markers, active hepatitis, trauma, or demonstrable prothrombotic markers other than those expected in SCD or Thal were not detected. In none of the Thal cases was a thrombotic history elicited but the SCD patient had a history of retinal artery and renal artery thrombosis (1 year previously). Discussion.A case series of this serious complication has not been previously reported. The known prothrombotic tendency in SCD and Thal is the most likely risk factor as other risk factors were absent. Thal cases were transfusion dependent, where thrombosis risk is generally about a quarter of that in non transfusion dependent Thal (Cappellini, Blood Reviews, 265, 2012, S20–23). In the SCD case, the prior history of arterial thrombosis, consistent with an embolic etiology, led us to examine whether a patent foramen ovale (PFO) was present, which was confirmed by bubble jet studies. This was subsequently closed. In patients with a history of embolic thrombosis, the presence of PFO should be sought and closure considered. Two cases were treated with Methylprednisolone soon after presentation. Two cases were commenced on Aspirin 75mg once a day to limit extension and as secondary prevention. The use of thrombolytic agents such as tissue thromboplastin activator have not been described in AST. In conclusion, spinal cord ischemia should be considered when facing a Thal or SCD patient with acute neurological symptoms affecting legs or bladder. This may be more common in hemoglobin disorders than is apparent from the literature.TableCase 1Case 2Case 3Case 4Age at presentation24373227GenderMaleMaleFemaleFemaleDiagnosisSCDThal MajorThal MajorThal MajorPresentation symptomsBilateral leg weakness ParaparesisParaplegia Urine retentionSacral paraesthesia Urine retentionLower limb pain paraesthesia, & weakness Urine retentionMRI findingsFusiform cord swelling (T9, T10) Secondary to ischemiaHigh T2 signal (T6 to conus) Swollen cord from T9Low cord signal(T11 - T12) Intramedullary syrinx (T4/5 - T7/8)1stScan: normal Repeat: High T2 posterior dorsal signal to T9 Conus medullary edemaExtramedullary haematopoiesisNoYes but no cord compressionNoNoHb (g/L)8013211389Plt (× 109/L)451191474438WBC (× 109/L)12.75.112.77.7NRBCs (%)0.39NDND0.5TransfusionNoYesYesYesLast transfusionNone− 2 days− 19 days− 20 daysSplenectomyNoNoYesNoPrior thrombosisYesNoNoNoOther risk factors*NoNoNoNoND = not detected.*Autoimmune markers, active hepatitis C, prothrombotic screen - non contributory. Disclosures:Cappellini:Novartis Pharmaceuticals: Research Funding.

Endocrine disorders in pregnancy: Selected highlights from the medical complications in pregnancy, 31st October - 2nd November 2011, London, UK

This course has been run annually for the past seventeen years. It encompasses reviews and updates in the management of medical problems that obstetric physicians and obstetricians can encounter in their practice. There were 120 delegates to this course from different countries around the world. Over three days, internationally renowned experts in obstetric medicine considered a wide range of topics such as thyroid disease and other endocrine disorders, connective tissue disorders, diabetes, sickle cell disease, asthma, neurology disorders, renal diseases and heart diseases. We chose to reflect on some of the endocrine- related topics to present a brief summary rather than go through the full curriculum.

Religious coping and hospital admissions among adults with sickle cell disease

Although a well-established literature implicates religiosity as a central element of the African American experience, little is known about how individuals from this group utilize religion to cope with specific health-related stressors. The present study examined the relation between religious coping and hospital admissions among a cohort of 95 adults with sickle cell disease-a genetic blood disorder that, in the United States, primarily affects people of African ancestry. Multiple regression analyses indicated that positive religious coping uniquely accounted for variance in hospital admissions after adjusting for other demographic and diagnostic variables. Specifically, greater endorsement of positive religious coping was associated with significantly fewer hospital admissions (β=-.29, P<.05). These results indicate a need for further investigation of the roles that religion and spirituality play in adjustment to sickle cell disease and their influence on health care utilization patterns and health outcomes.

Clinical, hematologic and molecular variability of sickle cell-β thalassemia in western India

BACKGROUND:Sickle cell-β thalassemia (HbS-β thalassemia) is a sickling disorder of varying severity, which results from compound heterozygosity for sickle cell trait and β thalassemia trait. The present study was undertaken to determine the genetic factors responsible for the clinical variability of HbS-β thalassemia patients from western India.MATERIALS AND METHODS:Twenty-one HbS-β thalassemia cases with variable clinical manifestations were investigated. The α and β globin gene clusters were studied by molecular analysis.RESULTS:Thirteen patients showed milder clinical presentation as against eight patients who had severe clinical manifestations. Four β thalassemia mutations were identified: IVS 1-5 (G→C), codon 15 (G→A), codon 30 (G→C) and codon 8/9 (+G). α thalassemia and XmnI polymorphism in homozygous condition (+/+) were found to be common among the milder cases. The βS chromosomes were linked to the typical Arab-Indian haplotype (#31). Framework (FW) linkage studies showed that four β thalassemia mutations were associated with different β globin gene frameworks. Linkage of codon 15 (G→A) mutation to FW2 is being observed for the first time.CONCLUSION:The phenotypic expression of HbS-β thalassemia is not uniformly mild and α thalassemia and XmnI polymorphism in homozygous condition (+/+) are additional genetic factors modulating the severity of the disease in the Indian subcontinent.

Neutropénie et/ou thrombopénie associée(s) à une infection aiguë par le parvovirus B19

Erythema infectiosum (fifth disease) is the most common clinical presentation of acute parvovirus B19 infection in infancy. In healthy adults, most cases of infection are asymptomatic or accompanied by a flu-like syndrome like headaches and myalgia. Haematological manifestations are dominated by transient aplasia of erythroid progenitor cells which remains asymptomatic in most of non immunocompromised patients. Patients with sickle cell disease, thalassemia or other disorders associated with shortened red blood cell survival are at particular risk for marked anemia or red blood cell aplasia. In immunosuppressed patients, anemia may be chronic because of persistent viral load. Neutropenia, lymphopenia or thrombocytopenia have also been reported in acute parvovirus B19 infection. Mechanisms of these cytopenias are not yet elucidated. We present two patients with thrombopenia and/or neutropenia but without anemia due to acute parvovirus B19 infection.

The spleen in the sickling disorders: an update

In early life, patients with sickle cell disease (SCD) can have acute, life-threatening emergencies related to splenic hypofunction (overwhelming bacterial sepsis), as well as anemic crises from acute splenic sequestration because of sudden pooling of blood in the spleen. The landmark penicillin prophylaxis study in 1985 showed a remarkable decrease in mortality from sepsis in young children with SCD who were treated with oral penicillin prophylaxis compared to placebo. Since that study, newborns are screened for SCD and placed on oral penicillin prophylaxis in nearly all of the United States, as well as in other countries where the disease is highly prevalent. The previously described permanent, complete and nearly universal "autosplenectomy" emerging by late childhood or early adulthood is now challenged by recent findings of reversibility of splenic dysfunction by the antisickling drug hydroxyurea or by successful allogeneic stem cell transplantation, even in older patients. Imaging techniques for hypofunction of the spleen are the most commonly used modalities to guide the clinician in decisions regarding medical or surgical management.

Assessing small airways disease

The manifestations of the sickling disorders are becoming increasingly familiar to clinicians in Great Britain. One of these disorders, sickle-cell haemoglobin disease, has hitherto received little attention, being regarded as a relatively mild condition. This paper describes some of the distinctive clinical features of the disease as seen in a series of nine cases which have recently presented in London, two of which were fatal. The special hazards of the condition in relation to pregnancy, air travel, and general anaesthesia are discussed.

The Landscape of Thrombophilia in Sickling Disorders: Unfamiliar Terrain.

Sickling disorders have long been suspected of decreasing physiologic thresholds for thrombosis, and the sickling process in tissue of being abetted by elements of the hemostatic system. The landscape of the presumed hypercoagulable state, however, has been ill-defined and differences among sickling disorders with regard to its characteristics, if any, undelineated. Learning how this landscape may reflect the pathophysiology of the sickling process may help guide further study of the interactions among the vasculature and the varieties of abnormal erythrocytes resulting from these hemoglobinopathies and define new opportunities to ameliorate the clinical manifestations of "sickle cell disease."Methods: Using laboratory strategies developed to characterize thrombophilia in non-sickling patients with thrombosis, modified for a largely non-European population, 144 patients with sickling disorders were prospectively evaluated for predisposition to thrombosis. A standard group of hemostatic studies was performed using patient samples obtained during steady-state "non-sickling" conditions, by skilled venepuncturists working consistently with this patient group.Genotypes included: HbSS 96/144 (67%); Hb SC 26/144 (18%;) Hb SSTh; 14/144 (9.5%); Hb S/AThal 8/144 (5.5%). 49/144 (34%) patients (pts) received regular automated erythrocytapheresis for prior stroke, recurrent acute chest syndrome or severe pain episodes > 6/yr.Results: As expected, 2/144 (1.4%) of pts were heterozygous for the Factor V Leiden mutation, 0/144 for the Prothrombin 20210 mutation, and 20/144 (14%) heterozygous, 1/144 (<1%) homozygous for the MTHFR C677T mutation despite homocysteine levels > 12 ng/dL in 38/144 patients (26%). Protein S activity levels were <65% in 83/144 (58%) pts with commensurate free Protein S levels. Total Protein S levels varied widely with no correlation to sickling genotypes, suggesting -as with homocysteine levels -dietary variation. Hb SC genotype was strongly associated with von Willebrand antigen (vWA) levels > 175%, frequently with lesser vWFactor activity (vWF) levels, whereas Hb SSt and SThal more frequently exhibited normal vWA/vWF profiles. Factor VIII activity varied widely, exhibiting no correlation to vWF antigen or activity levels in any of the Hb genotypes. Other thrombophilic conditioners, e.g. antithrombin III activity/Ag, Factor VIII activity, plasmnogen activator inhibitor, and b2-glycoprotein I antibodies were either normal or varied as expected in a " normal," e.g European population, with no correlation to Hb genotype.Conclusions: Thrombophilia in patients with sickling disorders appears to have varied contributors: Hb SC appears most thrombophilic with levels of vWF antigen suggestive of vascular dysfunction and supportive of intravscular platelet adhesion a aggregation. Other genotypes exhibit variable phenotypes, with Hb SThal exhibiting the least thrombogenic phenotype from a aboratory assessment perspective. vWF antigen and Protein S abnormalities emphasize the likely role of inflammation and vascular dysfunction but the dysjunction of vWF and Factor VIII activity hint at greater complexity. Further study of these phenomena and the inclusion of platelet function studies may yield additional insights as to the interaction of sickling erythrocytes, their products and vascular/hemostatic interactions. For now, routine thromboprophylaxis in patients with SC disease appears essential, and likely important in all other genotypes except Hb SThal.

The Occurrence of Four Globin Abnormalities in One Individual: Hb SC Disease with Hb Chicago and Deletional Alpha Thalassemia.

The occurrence of multiple globin abnormalities in one individual is not very rare, particularly in populations where hemoglobinopathies are common. In most cases, this is of genetic interest and may pose a diagnostic challenge due to the interaction of the products of mutant α and β globin genes and the presence of hybrid hemoglobins. Co-inheritance of α globin variants with sickle cell disease (Hb SS or SC) could have an effect on the disease phenotype particularly when the variant in question has altered functional properties (decreased or increased oxygen affinity) or stability. We report a patient with Hb SC disease with co-inheritance of the α chain variant, Hb Chicago (α136Leu→Met), and deletional α thalassemia (−α3.7) in trans to the Hb Chicago mutation. The patient is a 3-year old African-American male referred to the Pediatric Sickle Cell Clinic from the local Health Department. He is the product of an uneventful term pregnancy and a normal labor. He presented with seizures at age 3 weeks and underwent a neurologic evaluation which failed to reveal any abnormality. His subsequent course was uneventful without further seizures after 1 year of age and no hospitalizations. Physical exam was unremarkable with normal growth. A CBC showed Hb of 11.3 g/dl, Hct 35.2%, MCV 64.8 fl, MCH 20.8, MCHC 32.1, RDW 18.4%, retic count of 1.7% (absolute retic count of 92,480). Cation exchange HPLC revealed a Hb F of 6.8%, A2 3.3%, Hb S 33.1% and Hb C 30.0%. Both Hb S and Hb C peaks were followed by an additional peak of 13.2% (Hb SX) and 13.6% (Hb CX) respectively suggesting the presence of an α chain variant. The total quantity of Hb S was 46.3% (Hb S+Hb SX) and that of Hb C was 43.6% (Hb C+ Hb CX), whereas Hb X amounted to 26.8%. A reversed phase HPLC confirmed the presence of an α chain variant, which eluted earlier than normal α chains; αX constituted 37.5% of the total α chains. Sequencing of the β-globin gene confirmed the presence of Hb S (GAG→GTG) and Hb C (GAG→AAG) mutations in codon 6. A PCR for α globin deletions confirmed heterozygosity for the -α3.7 deletion. α globin sequencing revealed an apparent homozygosity for a CTG→ATG (Leu→Met) substitution of the codon 136 in α2 globin gene; this “apparent” homozygosity is due to the -α3.7 deletion in trans. Family studies showed that the patient's mother had Hb C trait with heterozygous α-thalassemia; the father was not available. The paternal grandmother had normal α-globin gene numbers, with heterozygous Hb Chicago, which was quantitated at 20.7%. Thus, the patient's genotype was ascertained as βS/βC;-α/αChicagoα. Hb Chicago has been reported in conjunction with Hb SS but not with Hb SC disease. The co-inheritance of the α-chain variant, Hb G-Philadelphia (α68Asn→Lys) and Hb SC disease, has been reported by Lawrence et al (Blood 90:2819–25, 1997); this combination resulted in the acceleration of Hb C crystal formation and decreased Hb S polymerization with a resultant mild sickling disorder. α136 is a heme contact; the Leu→Met substitution in Hb Chicago does not alter the functional properties or the stability of the molecule and is not associated with any hematologic abnormalities in heterozygous carriers. This residue is not involved in intermolecular contacts of deoxy Hb S and hence is not expected to alter the kinetics of deoxy Hb S polymerization. The significance of this observation is the accurate diagnosis of the complex Hb phenotype and ascertainment of its lack of interaction with the sickling or crystallization process.

Sickle Cell Disease

1. M. Catherine Driscoll, MD* 1. *Director, Hematology Program, Children's Hospital at Montefiore, Bronx, NY After completing this article, readers should be able to: 1. Describe the pathogenesis of sickle cell disease. 2. Delineate the complications of sickle cell disease and their management. 3. Review guidelines for health maintenance and preventive measures. 4. Discuss the current treatments for sickle cell disease. Sickle cell disease (SCD) is a chronic hemolytic anemia that includes the hemoglobin (Hb) variants SS, SC, S-beta thalassemia, SO Arab, SD, and other rare S-Hb genotypes. SCD is one of the most common genetic diseases worldwide. Sickle disorders are seen commonly in sub-Saharan Africa but also occur in the Mediterranean, India, and the Arabian Peninsula. The geographic distribution of sickle hemoglobinopathies corresponds to the distribution of malaria; indeed, the sickle gene in the heterozygote (AS) form protects against death from endemic Plasmodium falciparum malaria infection. In addition, the clinical manifestations of SCD vary among these geographic sites, with individuals from India, the Arabian Peninsula, and Senegal having milder disease than those from parts of Africa. This pattern suggests that genetic modifiers ameliorate the disease in certain populations and contribute to the significant variation in clinical manifestations. The presence of SCD in North, South, and Central America is due to immigration patterns and represents primarily the more severe African types. The genetic defect producing sickle Hb is a single nucleotide substitution (GTG for GAG) at codon 6 of the beta globin gene on chromosome 11 that results in the substitution of valine for glutamic acid. This hydrophobic amino acid substitution allows Hb S to polymerize on deoxygenation, and multiple polymers bundle to form rodlike structures that distort the red cell into the classic crescent shape. Sickled red cells are less deformable in the microcirculation and provoke a cascade of events that results in vascular occlusion, organ ischemia, and eventually, chronic end-organ damage. The ancillary events of polymerization that …

Sickle cell disease caused by Hb S/Québec‐CHORI: Treatment with hydroxyurea and response

Sickle hemoglobin (Hb S;betaGlu 6 Val) is due to an A>T transversion in codon 6 of the beta-globin gene. Other variant hemoglobins mimic Hb A, S, or C on newborn screening and clinical laboratory diagnostic tools, thus making their correct identification potentially difficult. Sickling disorders can result in individuals who are compound heterozygous for beta-globin mutations (e.g., Hb SC, HbSO(Arab)). The authors report a second case of HbS/Québec-CHORI, a severe compound heterozygous sickling disorder and their experience managing this patient with hydroxyurea.

Sickle cell–haemoglobin E (HbSE) compound heterozygosity: a clinical and haematological study

The paucity of clinical reports in the world literature suggests that, as a disease entity, haemoglobin SE compound heterozygosity is of negligible importance. In view of the significant community prevalence of this haemoglobinopathy in the Sultanate of Oman where it is the second most prevalent sickling disorder, a hospital study of 12 SE compound heterozygotes from six unrelated Arab families was undertaken to determine their clinico-haematological features. Our findings were compared with those reviewed in the literature. Clinical and haematological evaluation was carried out by conventional methods including chromatographic haemoglobin analysis. At least 50% of those studied were asymptomatic throughout the study period but sickling-related complications occurred in the rest and included the acute chest syndrome (1/12), severe vaso-occlusive skeletal pain (2/12), frontal bossing (1/12) possibly indicative of significant chronic haemolysis and recurrent infections of the urinary tract (1/12). Steady-state haemoglobin levels fell within the reference range while MCV and MCH values were, as expected, reduced in most cases; nevertheless, concomitant inheritance of alpha-thalassaemia trait was also likely. Red cell morphology was striking by the absence or rarity of pseudo-sickled cells in the blood films of many patients during the steady state and in crises. Bearing in mind the prevalence of 0.05% of SE compound heterozygosity in Oman, the findings in this single study of the largest number of SE patients and their relatives confirm the predominantly asymptomatic nature of this sickling disorder in individuals in the community at large. HbF levels do not appear to explain the heterogeneous nature of this haemoglobinopathy. Correlation of the variable clinical and haematological features of SE cases with their alpha-globin gene status and beta-cluster haplotypes (linked to the beta(s)- and beta(e)-genes) merits a separate investigation, which is being currently organized.

Hyperbaric oxygen therapy in a case of combined sickle cell and hemoglobin Lepore disease

*Hematology Division, Department of Oncology, Transplant and New Technologies in Medicine, University of Pisa, Pisa, Italy; † Emergency Department, Hyperbaric Therapy Center, Pisa University Hospital, Pisa, Italy Dear Sir, The management of hemoglobin disorders still represents a major clinical challenge. Sickle cell anemia and related disorders, including sickle cell thalassemia disease, are almost unequivocally complicated by multiorgan damage and characterized by recurrent crises. Therapeutic approaches are not curative and a carefully evaluated transfusion program is frequently necessary, especially in critical situations such as surgery. Conflicting results about the use of hyperbaric oxygen therapy in acute sickle cell crisis have been reported. 1,2 To date, there are no conclusive studies defining the possible benefits of this therapeutic approach. The management of sickle cell anemia essentially involves aspirin administration and the treatment of complications as they arise. Transfusions are not usually required except in special circumstances such as stroke or intractable, frequently recurring, painful crises. Transfusions may be used for the repair of leg ulcers. One very large study, however, found no difference in healing rates associated with any particular therapeutic modality. 3

Glomerular Involvement in Adults with Sickle Cell Hemoglobinopathies

Patients with sickle cell anemia (SCA) may develop a glomerulopathy with proteinuria and progressive renal insufficiency, leading to ESRD. Albuminuria is a sensitive marker of glomerular damage in this population and precedes the development of renal insufficiency. For determination of the prevalence of glomerular damage in SCA and the clinical correlates of renal insufficiency, 300 adult patients with SCA were studied (hemoglobin SS = 184; and 116 with other sickling hemoglobinopathies: SC, SD, and S-beta thalassemia); albumin excretion rates (AER) and renal function (Cockroft-Gault formula) were determined, and clinical and hematologic evaluations were conducted. In hemoglobin SS disease, increased AER (micro- and macroalbuminuria) occurred in 68% of adult patients, and macroalbuminuria occurred in 26%. In other sickling disorders, increased AER occurs in 32% of adults, and macroalbuminuria occurs in 10%. The development of graded albuminuria was age dependent, so at 40 yr, 40% of patients with SS disease had macroalbuminuria. There were no differences in hematologic parameters (hemoglobin levels, white blood cell count, percentage of reticulocytes, platelet counts, or lactate dehydrogenase levels) between patients with normoalbuminuria and those with micro- or macroalbuminuria. By multivariate analysis, albuminuria correlated with age and serum creatinine in SS disease but not with BP or hemoglobin levels. In other sickling disorders, albuminuria tended to be associated with age but not with hemoglobin or BP levels. The diastolic BP was lower in patients with SCA than in African American control subjects, and the development of renal insufficiency, which was present in 21% of adults with SS disease, was not accompanied by significant hypertension. It is concluded that glomerular damage in adults with SCA is very common, and a majority of patients with SS disease are at risk for the development of progressive renal failure. The development of micro- and macroalbuminuria is not related to the degree of anemia, suggesting that sickle cell glomerulopathy is not solely related to hemodynamic adaptations to chronic anemia. In contrast to other glomerulopathies, the development of systemic hypertension is uncommon in SS disease with renal insufficiency.

Hydroxyurea Treated Sickle Disorders Demonstrate Decreased Plasma Hb, Red Cell Vesicles and Thrombolysis.

Free plasma Hb has been recently implicated in the genesis of pulmonary hypertension in sickle cell disorders (SCD) through a putative NO scavenging mechanism. We have recently reported that free plasma Hb is correlated with increased plasma red cell derived vesicles (RBVes) in sickle cell and thalassemia disorders (Westerman, Blood 2004; 104:1671). Since high levels of HbF have been associated with decreased elevation of RBVes in children with SCD (Setty Blood 2000; 96:1119–1124), we hypothesized that patients treated with hydroxyurea (HU) might show a similar normalisation of RBVes. Given our finding of an association between RBVes and free plasma Hb, such treatment might also be predicted to correct increments in free plasma Hb. In this study we have examined whether sickle cell patients treated with HU show evidence of a decrease in free plasma Hb and RBVes compared to untreated SCD patients. RBVes, free plasma Hb, and markers of activation of thrombolysis were quantitated. 35 adult SCD patients, 27 in steady state, untransfused and not receiving HU and 7 patients on long term HU at a dose of 10–30 mg/kg/day. These parameters were also measured in 27 healthy control subjects without SCD. RBVes were significantly higher in untreated SCD (15.59±3.07 x 103/μL of blood) than in control subjects (2.13 ± 0.5)(p=0.001). In HU-treated SCD patients, vesicles were significantly lower (3.97±0.83)(p=0.0371). than in untreated patients and approached levels found in healthy controls. Free plasma Hb was significaly increased in untreated SCD (16.74±3.87) compared with healthy controls (1.77±0.2)(p=0.001); these levels were also corrected in HU treated SCD patients (13.42±4.48). The proportion of RBVes expressing phosphatadyl serine was also lower in HU-treated SCD (37.25± 9.79) than in untreated SCD (52.52±4.74). This was paralleled by a decrease in red cells expressing PS in HU treated patients (11.83± 3.95) compared with untreated patients (42.71±8.45)(p=0.011). This decrease in both RBVes and RBCs expressing PS in HU-treated patients might in principle decrease activation of coagulation. Indeed, plasma Ddimers, which are increased in untreated SCD (480 ±60.14) compared with healthy controls (117.43±38)(p=0.018). are normalised in HU treated patients (190±28.69). These data provide evidence of a link between RBVes and plasma Hb and suggest that PS expression on RBVes and red cells plays a role in the prothrombotic state seen in SCD. As HU treatment appears to correct plasma Hb, long term treatment may be associated with a decreased scavenging of NO and hence the risk of pulmonary hypertension. The correction of the prothrombotic tendency may also be beneficial in this regard. Prospective trials are indicated to confirm whether HU treated patients have evidence of decreased risk of pulmonary hypertension.

MP4, a Human Hemoglobin Modified with Maleimide-Peg, Reduces Sickling of Red Blood Cells in an In Vitro Model.

Human hemoglobin surface-modified with maleimide polyethylene glycol (MP4) has been shown to be effective in transporting O2 and maintaining tissue perfusion in several animal models. MP4 appears to be free of vasoconstriction, and clinical trials have shown MP4 to be free of the side-effects commonly associated with hemoglobin-based products. Since MP4 is effective in delivering O2 to capillaries in the hamster microcirculation, our hypothesis is that it would be of therapeutic benefit in Sickle Cell Disease. In order to test this hypothesis, we measured pressure that develops as dilute sickle cells pass through a filter with and without MP4. Cells from patients with sickling disorders were washed with phosphate-buffered saline (PBS) containing 1% bovine serum albumin (BSA) and suspended at 1% hematocrit in the presence and absence of MP4 (2 g/dL). The suspension was then pumped through a hollow fiber oxygenator (Living Systems Instrumentation, Model Number OXR) using an array of 162 polypropylene fibers, 300 mm OD, 240 mm ID, surface area 0.0115 m2. After emerging from the oxygenator the suspension passed through a filter (Millipore Isopore, pore size 5.0 mm, 13 mm diameter) at a pump rate of 1 mL/min. All experiments were performed at 21oC. After achieving a steady flow rate, the oxygenator gas was abruptly changed to N2, and the PO2 and pressure of the prefilter suspension was continuously monitored. As PO2 fell, pressure began to rise in all experiments, but in the presence of MP4, the pressure rise was offset, being lower by about 10 mm Hg, indicating a favorable effect on sickling at constant PO2. If MP4 was saturated with CO, sickling was inhibited, even in the absence of O2. These results indicate that MP4 has a significant effect on sickling, apart from any effect it might have in promoting capillary perfusion. Furthermore, the results confirm that despite its low P50 (~5 mm Hg), MP4 does not “steal” O2 from sickle cells. Supported by grants HL64395 and HL076163 from the NHLBI

Sickle Cell and Anesthesia: Do Not Abandon Well-established Practices without Evidence

Hemoglobin: Structure and Function Hemoglobin (Hb) is composed of two pairs of sub-units containing protoheme and globin.. The various globin chains differ in the number and sequence of amino acids and are designated by α, β, γ, δ, e, ζ, and θ. Normal adult RBCs have three types of hemoglobin: HbA (α2,β2) approx. 95%, HbA2 (α2δ2) approx. 2.5 %, and HbF (α2γ2). The spatial relationship of the four subunits determines oxygen affinity as well as physical properties such as Hb solubility and stability. At birth red cells contain 70-90 % HbF until 2-4 months of age. Beta chain production begins shortly before birth and gamma chain production wanes resulting in a normal adult profile by age 4 months. Thus disorders of the beta chain will not manifest themselves in the first few months nor be identified by precipitation screening tests. Hemoglobinopathies can result from either production of an abnormal hemoglobin chain or by under production of a given chain. The most common mechanism of the former type is the result of a single substitution of one amino acid for another on the protein chain, which occurs with sickling disorders. Underproduction of a given chain results in a group of disorders known as thalassemias.

Thalassemia and related hemoglobinopathies

Hemoglobinopathies are the most common single gene disorders in man. There are several hundred of these disorders though the thalassemias -- alpha and beta and the sickling disorders make up the vast majority. Recent advances in the understanding of the hemoglobin structure and the genetics of its synthesis has contributed significantly to the understanding of these diseases. Disorders include those with reduced globin synthesis, abnormal globin chains and failure to switch globin chain synthesis at the appropriate age. This review focuses on the clinical features, diagnosis and management strategies of the alpha and beta thalassemias, the sickling disorders and touches on a few rarer hemoglobinopathies. It also emphasizes prevention strategies and chronic transfusion safety in countries like India where there are limited resources.

Adults with Severe Sickle Cell Anaemia and Iron Overload Have a High Incidence of Osteopenia and Osteoporosis.

Background: There is very little published data on osteopenia or osteoporosis in patients with sickle cell disorders (SCD) with only occasional case reports that have noted osteopenia in individual SCD patients. It is known that individuals of Afro-Caribbean decent have on average higher BMD scores then age matched Caucasian controls. The causes for bone demineralisation in SCD may be multifactoral. Putative contributory mechanisms include; marrow expansion, bone infarction, delayed puberty from anaemia, low vitamin D, iron overload from blood transfusion, iron chelation therapy, and hypogonadism.Methods and Findings: 17 consecutive SCD patients who had previously been transfused or were currently on a transfusion programme underwent DEXA scanning using a Hologic QDR 4500A. Hypogonadism was assessed for in all patients as well as Vitamin D3, parathyroid hormone (PTH), serum ferritin and haemoglobin levels. 11 of the 17 patients had undergone MRI to assess liver iron. Of 10 females, 6 had osteopenia (Z >−1.0, n= 4) or osteoporosis ( Z >−2.0, n=2) in the spine compared to age matched caucasian controls (p=0.008). In contrast, only 4 had significant hip demineralisation; 2 patients had osteoporosis and 2 were osteopenic. All patients with hip osteopenia also had spinal osteopenia. Liver iron concentration was significantly higher in the osteopenic (9.4mg/g dry wt) than the non-osteopenic group (1.95mg/g dry wt) (p=0.01). Mean serum oestradiol levels were no different between the osteopenic (235 pmol/L) and the non osteopenic patients (287 pmol/L). No differences in ferritin, units of blood transfused, parathyroid hormone or vitamin D level were seen. Only 2 females had received iron chelation with deferrioxamine one of whom was osteopenic. Among 7 males, 2 had spinal osteopenia (mean Z score −1.4) (p= 0.05) but none had osteopenia of the hip. The liver iron was higher in the osteopenic males (mean 12.9 mg/g dry weight) than in the non osteopenic group (mean 2.32 mg/g/dry weight) (p <0.05). Serum ferritin was also higher in osteopenic patients (mean 3729ug/l) than the non-osteopenic group (mean 745ug/l) (p=0.008). No significant difference between the serum testosterone and units of blood transfused, parathyroid hormone or vitamin D level was seen. Only one of the patients had received iron chelation and he was not osteopenic. Among all patients together, there was no evidence on MRI of increased cardiac iron but there was evidence of hypogonadothrophic hypogonadism is 1 female, while the remainder were not hypogonadal. There was evidence of disturbance of the Calcium- Vitamin D- PTH axis in 2 patients (1 male,1 female) both of whom were osteopenic.Conclusion: Osteopenia is a surprisingly common in adult patients with sickle disorders; 47% of patients had osteopenia. Iron loading may be a relevant contributing factor as liver iron was significantly greater in osteopenic than non-osteopenic patients. Hypogonadism and iron chelation therapy can be reasonably excluded as contributory facors in most patients but should be monitored in all patients on transfusion programmes.