Comparison of sickle cell-beta0 thalassaemia with homozygous sickle cell disease

Clinical, laboratory, and molecular characteristics of a cohort of children with hemoglobinopathy S/beta-thalassemia

INTRODUCTION

Hemoglobinopathy Sβ-thalassemia (HbSβ-thal) has a wide range of clinical and laboratory severity. There is limited information on the natural history of HbSβ-thal and its modulating factors. We described the molecular, hematological, and clinical characteristics of a cohort of children with HbSβ-thal and estimated its incidence in Minas Gerais, Brazil.

METHODS

Laboratory and clinical data were retrieved from medical records. Molecular analysis was performed by HBB gene sequencing, PCR-RFLP, gap-PCR, and MLPA.

RESULTS

Eighty-nine children were included in the study. Fourteen alleles of β-thal mutations were identified. The incidence of HbSβ-thal in the state was 1 per 22,250 newborns. The most common βS-haplotypes were CAR and Benin. The most frequent βthal-haplotypes were V, II, and I. Coexistence of 3.7 kb HBA1/HBA2 deletion was present in 21.3 % of children. β-thalassemia mutations were associated with several clinical and laboratory features. In general, the incidence of clinical events per 100 patient-years was similar for children with HbSβ0-thal, IVS-I-5 G>A, and IVS-I-110 G>A. Children with HbSβ+-intermediate phenotypes had a more severe laboratory and clinical profile when compared with those with HbSβ+-mild ones. βS-haplotypes and α-thalassemia did not meaningfully influence the phenotype of children with HbSβ-thal.

CONCLUSION

The early identification of β-thalassemia alleles may help the clinical management of these children.

Complete Neurologic Recovery of Cerebral Fat Embolism Syndrome in Sickle Cell Disease

Sickle cell disease is one of the most common inherited hemoglobinopathies diagnosed in the United States. Patients often present with severe anemia, pain crises, infections, and vaso-occlusive phenomena. Complications of these disorders can lead to significant debilitating morbidity and mortality. Fat embolism syndrome (FES) is a rare and devastating complication of sickle cell disease. It usually presents with a rapidly deteriorating clinical course, and the prognosis is dismal. We report a case of FES in a 19-year-old African American male with a history of sickle cell disease who presented with tonic-clonic seizures and was found to have multi-organ failure. FES was diagnosed 20 days from a presentation based on blood cytopenias and magnetic resonance imaging findings that were obscured at the initial presentation. We describe in this report, the patient’s course from presentation until diagnosis and resolution. Our case is peculiar as the patient had a very good outcome without the need for red blood cell (RBC) exchange; instead, supportive treatment and simple RBC transfusions were enough to change the clinical course of this almost fatal syndrome.

The protective effect of the spleen in sickle cell patients. A comparative study between patients with asplenia/hyposplenism and hypersplenism

Sickle cell disease (SCD) is caused by a point mutation in the beta-globin gene. SCD is characterized by chronic hemolytic anemia, vaso-occlusive events leading to tissue ischemia, and progressive organ failure. Chronic inflammatory state is part of the pathophysiology of SCD. Patients with SCD have extremely variable phenotypes, from mild disease to severe complications including early age death. The spleen is commonly injured in SCD. Early splenic dysfunction and progressive spleen atrophy are common. Splenomegaly and hypersplenism can also occur with the loss of the crucial splenic function. Acute, life-threatening spleen-related complications in SCD are well studied. The association of laboratory parameters with the spleen status including hyposplenism, asplenia, and splenomegaly/hypersplenism, and their implication in vaso-occlusive crisis and long-term complications in SCD remain to be determined. We evaluated the association between the spleen status with clinical and laboratory parameters in 31 SCD patients: Group a) Patients with asplenia/hyposplenism (N = 22) (including auto-splenectomy and splenectomized patients) vs. Group b) patients with splenomegaly and or hypersplenism (N = 9). Laboratory studies included: Complete Blood Count, reticulocyte count, iron metabolism parameters, C Reactive Protein (CRP), Hb variant distribution, and D-dimer. Metabolic and morphological red blood cell (RBC) studies included: density gradient (by Percoll), glucose consumption, lactate release, and K⁺ leakage, fetal RBC (F-Cells) and F-Reticulocytes, annexinV+, CD71⁺, oxidative stress measured by GSH presence in RBC and finally Howell Jolly Bodies count were all analyzed by Flow Cytometry. Scanning electron microscopy analysis of RBC was also performed. Patients with asplenia/hyposplenism showed significantly higher WBC, platelet, Hematocrit, hemoglobin S, CRP, D-dimer, Gamma Glutamyl Transferase (GGT), cholesterol, transferrin, annexin V+ RBCs, CD71⁺ RBCs, together with a markedly lower F Reticulocyte levels in comparison with splenomegaly/hypersplenism patients. In summary, important differences were also found between the groups in the studied RBCs parameters. Further studies are required to elucidate the effect of the spleen including hyper and hypo-splenia on laboratory parameters and in clinical manifestations, vascular pathology, and long-term complications of SCD. The benefits and risks of splenectomy compared to chronic transfusion need to be evaluated in clinical trials and the standard approach managing hypersplenism in SCD patients should be re-evaluated.

Calibration of T2 oximetry MRI for subjects with sickle cell disease

PURPOSE

Cerebral T₂ oximetry is a non-invasive imaging method to measure blood T₂ and cerebral venous oxygenation. Measured T₂ values are converted to oximetry estimates using carefully validated and potentially disease-specific calibrations. In sickle cell disease, red blood cells have abnormal cell shape and membrane properties that alter T₂ oximetry calibration relationships in clinically meaningful ways. Previous in vitro works by two independent groups established potentially competing calibration models.

METHODS

This study analyzed pooled datasets from these two studies to establish a unified and more robust sickle-specific calibration to serve as a reference standard in the field.

RESULTS

Even though the combined calibration did not demonstrate statistical superiority compared to previous models, the calibration was unbiased compared to blood-gas co-oximetry and yielded limits of agreement of (-10.1%, 11.6%) in non-transfused subjects with sickle cell disease. In transfused patients, this study proposed a simple correction method based on individual hemoglobin S percentage that demonstrated reduced bias in saturation measurement compared to previous uncorrected sickle calibrations.

CONCLUSION

The combined calibration is based on a larger range of hematocrit, providing greater confidence in the hematocrit-dependent model parameters, and yielded unbiased estimates to blood-gas co-oximetry measurements from both sites. Additionally, this work also demonstrated the need to correct for transfusion in T₂ oximetry measurements for hyper-transfused sickle cell disease patients and proposes a correction method based on patient-specific hemoglobin S concentration.

β-Thalassemia pathogenic variants in a cohort of children from the East African coast

BACKGROUND

β-Thalassemia is rare in sub-Saharan Africa. Previous studies have suggested that it is limited to specific parts of West Africa. Based on hemoglobin A2 (HbA2 ) concentrations measured by HPLC, we recently speculated that β-thalassemia might also be present on the East African coast of Kenya. Here, we follow this up using molecular methods.

METHODS

We used raised hemoglobin A2 (HbA2 ) values (> 4.0% of total Hb) to target all HbAA members of a cohort study in Kilifi, Kenya, for HBB sequencing for β-thalassemia (n = 99) together with a sample of HbAA subjects with lower HbA2 levels. Because HbA2 values are artifactually raised in subjects carrying sickle hemoglobin (HbS) we sequenced all participants with an HPLC pattern showing HbS without HbA (n = 116) and a sample with a pattern showing both HbA and HbS.

RESULTS

Overall, we identified 83 carriers of four separate β-thalassemia pathogenic variants: three β0 -thalassemia [CD22 (GAA→TAA), initiation codon (ATG→ACG), and IVS1-3' end del 25bp] and one β+ -thalassemia pathogenic variants (IVS-I-110 (G→A)). We estimated the minimum allele frequency of all variants combined within the study population at 0.3%.

CONCLUSIONS

β-Thalassemia is present in Kilifi, Kenya, an observation that has implications for the diagnosis and clinical care of children from the East Africa region.

Hb S/-Thalassemia in the REDS-III Brazil Sickle Cell Disease Cohort: Clinical, Laboratory and Molecular Characteristics

We described the clinical, laboratory and molecular characteristics of individuals with Hb S (HBB: c.20A>T)/β-thalassemia (Hb S/β-thal) participating in the Recipient Epidemiology and Donor Evaluation Study (REDS-III) Brazil Sickle Cell Disease cohort. HBB gene sequencing was performed to genotype each β-thal mutation. Patients were classified as Hb S/β⁰-thal, Hb S/β⁺-thal-severe or Hb S/β⁺-thal based on prior literature and databases of hemoglobin (Hb) variants. Characteristics of patients with each β-thal mutation were described and the clinical profile of patients grouped into Hb S/β⁰-thal, Hb S/β⁺-thal and Hb S/β⁺-thal-severe were compared. Of the 2793 patients enrolled, 84 (3.0%) had Hb S/β⁰-thal and 83 (3.0%) had Hb S/β⁺-thal; 40/83 (48.2%) patients with Hb S/β⁺-thal had mutations defined as severe. We identified 19 different β-thal mutations, eight Hb S/β⁰-thal, three Hb S/β⁺-thal-severe and eight Hb S/β⁺-thal. The most frequent β⁰ and β⁺ mutations were codon 39 (HBB: c.118C>T) and IVS-I-6 (T>C) (HBB: c.92+6T>C), respectively. Individuals with Hb S/β⁰-thal had a similar clinical and laboratory phenotype when compared to those with Hb S/β⁺-thal-severe. Individuals with Hb S/β⁺-thal-severe had significantly lower total Hb and Hb A levels and higher Hb S, white blood cell (WBC) count, platelets and hemolysis markers when compared to those with Hb S/β⁺-thal. Likewise, individuals with Hb S/β⁺-thal-severe showed a significantly higher occurrence of hospitalizations, vaso-occlusive events (VOE), acute chest syndrome (ACS), splenic sequestration, blood utilization, and hydroxyurea (HU) therapy.

EE score: an index for simple differentiation of homozygous hemoglobin E and hemoglobin E-β0-thalassemia

BACKGROUND

The objective of the study was to describe a formula based on hemoglobin (Hb)A2 and HbF levels for differentiation of homozygous HbE and HbE-β-thalassemia.

METHODS

A total of 1256 subjects suspected for homozygous HbE or HbE-β0-thalassemia were recruited at the ongoing thalassemia screening program at Khon Kaen University, Thailand. Hb analysis was done using capillary electrophoresis. Genotyping was based on DNA analysis. An arbitrary formula based on HbA2 and HbF was developed statistically for differentiation of the two conditions. Validation was carried out prospectively on another 139 subjects encountered at routine laboratory.

RESULTS

Among 1256 subjects, Hb and DNA analyses identified cases with homozygous HbE (n=1076, 85.7%), HbE-β0-thalassemia (n=140, 11.1%), HbE-δβ0-thalassemia (n=30, 2.4%) and unknown HbE-related disorder (n=10, 0.8%). An inverse correlation between the amounts of HbA2 and HbF in HbE-β0-thalassemia was observed. With differences in the amounts of HbA2 and HbF between the groups, an arbitrary score (7.3 HbA2+HbF) was developed where score above 60 indicated HbE-β0-thalassemia. Application of this score on another 139 subjects showed accurate prediction of HbE-β0-thalassemia with 100% sensitivity, 96.5% specificity, 85.7% positive predictive value and 100% negative predictive value. Successful application onto couples at risk was demonstrated.

CONCLUSIONS

An established score should prove useful in the differentiation of homozygous HbE and HbE-β0-thalassemia in routine setting and lead to a significant reduction in number of referring cases for molecular testing.

Coinheritance of B-Thalassemia and Sickle Cell Anaemia in Southwestern Nigeria

BACKGROUND

Genes for haemoglobin S are found in high frequencies in Nigeria. However, there is little information on beta thalassemia in sickle cell anaemia in this population. The clinical presentation of HbS- β thalassemia is enormously variable, ranging from an asymptomatic state to a severe disorder similar to homozygous sickle cell disease.

MATERIALS AND METHODS

Haemoglobin A2 and HbF were determined in sickle cell anaemia patients attending LAUTECH Teaching Hospital, Osogbo, by elution after electrophoresis and alkaline denaturation methods respectively. Haematological parameters were estimated using Sysmex KX-21N and percentage target cells using Leishman's staining technique.

RESULTS

Exactly 6% f the SCA patients were found to have elevated HbA2 (>3.3%) and HbF (>1.3%). These patients also had normal erythrocyte indices, increased platelet count, a significantly higher HCT and an increased % target cell.

CONCLUSION

These findings confirm that the frequency of beta thalassaemia in sickle cell patients in Nigeria is higher than previously thought. It is therefore important to consider the possibility of this variant in patients with sickle cell anaemia since their course may differ from that of patients with homozygous sickle cell anaemia.

Sickle cell disease in Madhya Pradesh, Central India: A comparison of clinical profile of sickle cell homozygote vs. sickle-beta thalassaemia individuals

BACKGROUND AND OBJECTIVES

The clinical manifestation in sickle cell disease (SCD) patients varies from one individual to another due to factors like the presence of alpha-thalassaemia mutation, foetal haemoglobin, and β-globin gene haplotype. The present study enumerates the clinical profile of sickle cell anaemia patients from Central India.

METHODS

Seven hundred seventy-six SCD patients from Jabalpur and surrounding districts (Madhya Pradesh) in central India were registered with the sickle cell clinic of NIRTH, Jabalpur. The present study reveals recorded signs and symptoms of genetically confirmed sickle cell anaemia (404) and sickle beta thalassaemia (92) patients.

RESULTS

Majority of the patients were from scheduled caste communities (47.9%) and Gond tribal community (13.8%). Splenomegaly was the most common clinical manifestation observed (71.4%). Overall, 63.5% patients had a history of blood transfusion. The most frequent signs and symptoms observed were Pallor, Icterus, Joint pain, Fever, and Fatigue. Majority of the patients revealed onset of disease prior to attaining the age of 3 years (sickle cell anaemia 44.3% and sickle beta thalassaemia 35.9%). Mean haemoglobin levels among SCA individuals were marginally higher than SBT patients. On the other hand, mean foetal haemoglobin levels among SBT individuals showed the reverse trend. Notably, the present study reports the first incidence of priapism recorded in Central India.

CONCLUSIONS

The study revealed a high prevalence of SCD among scheduled caste, backward caste, and tribal communities. Dissemination of study findings, screening, pre-marriage counselling, and pre-natal diagnosis are fundamental to preventing or lowering of birth of sickle cell anaemia children in the affected populations.

Association of alpha-thalassemia, TNF-alpha (-308G>A) and VCAM-1 (c.1238G>C) gene polymorphisms with cerebrovascular disease in a newborn cohort of 411 children with sickle cell anemia

Cerebrovascular disease (CVD) is a severe complication associated with sickle cell anemia. Abnormal transcranial Doppler (TCD) identifies some children at high risk, but other markers would be helpful. This cohort study was aimed at evaluating the effects of genetic biomarkers on the risk of developing CVD in children from Minas Gerais, Brazil. Clinical and hematological data were retrieved from children's records. Outcomes studied were overt ischemic stroke and CVD (overt ischemic stroke, transient ischemic attack, abnormal TCD, or abnormal cerebral angiography). Out of 411 children, 386 (93.9%) had SS genotype, 23 (5.6%) had Sβ(0)-thal and two had severe Sβ(+)-thal (0.5%). Frequency of CVD was lower in Sβ-thal group (p=0.05). No effect of VCAM-1 polymorphism on stroke or CVD risks was detected. Cumulative incidence of stroke was significantly higher for children with TNF-α A allele (p=0.02) and lower for children with HBA deletion (p=0.02). However, no association between CVD and TNF-α -308G>A was found. CVD cumulative incidence was significantly lower for children with HBA deletion (p=0.004). This study found no association between VCAM1 c.1238G>C and stroke. An association between stroke and TNF-α -308A allele has been suggested. Our results have confirmed the protective role of HBA deletion against stroke and CVD.

Characteristics of sickle cell anemia in Yemen

We studied 136 males and 105 females with sickle cell anemia to determine the characteristics of the disease in Yemen. Their mean age [± SD (standard deviation)] was 12.8 ± 9.5 years (range: 9 months-40 years). Taiz, Hudaydah and Hajjah governorates, in the South-Central and the Northwestern provinces, showed the highest prevalence. Eighty percent of the patients had family history of the disease, 73.0% patients had history of parental consanguinity and 20.7% of death of relative(s) due to the disease; 5.4% patients were older than 30 years of age. Pain, jaundice and infection were the most frequent features. Splenomegaly, cholelithiasis, osteomyelitis, acute chest syndrome (ACS), osteonecrosis and stroke occurred in 12.0, 9.5, 8.7, 6.6, 6.6 and 2.9%, respectively. Priapism and leg ulcers were rare. The mean laboratory values (obtained in the steady state) were: hemoglobin (Hb) 7.9 g/dL, WBC 14.08 × 10(9)/L, platelet 460 × 10(9)/L, reticulocytes 14.5%, lactate dehydrogenase (LDH) 597 U/L, Hb F (α2γ2) 16.69%, Hb S [β6(A3)Glu→Val, GAG>GTG] 77.31% and Hb A(2) (α2δ2) 1.47%, respectively. There was no significant difference between South-Central and Northwestern provinces regarding clinical events and hematological parameters.

Docetaxel-induced thrombotic thrombocytopenic purpura/hemolytic uremic syndrome-related complex in a patient with metastatic prostate cancer?

A 63-year-old African American man was diagnosed with prostate cancer by biopsy for elevated prostrate-specific antigen. He was initially treated with radiation and then with intermittent androgen ablation because of biochemical relapse. He continued to have rising prostrate-specific antigen and he was thought to have hormone-resistant prostate cancer. So he received chemotherapy with docetaxel. He returned to the hospital within 3 days of the first cycle of treatment with fever, altered mental status, acute renal failure, anemia, and thrombocytopenia. He was started on empiric antibiotics but his cultures from most sites were negative. His platelets dropped from 119,000 to a nadir of 10,000 during hospital stay. Patient had microangiopathic hemolytic anemia suggested by elevated lactate dehydrogenase, decreased haptoglobin, increased indirect bilirubin, and schistocytes in peripheral smear. His coagulation profile was normal. A presumptive diagnosis of chemotherapy-related thrombotic thrombocytopenic purpura (TTP)-hemolytic uremic syndrome was made and patient was started on fresh frozen plasma infusion and hemodialysis for renal failure and steroids. Patient improved symptomatically, platelet count was stable, and lactate dehydrogenase was in a declining trend after 5 days of fresh frozen plasma infusion. The ADAMS TS-13 activity was 37% suggestive of chemotherapy-related TTP. Patient also had sickle cell beta thalassemia disease and glucose 6 phosphate dehydrogenase deficiency. Docetaxel, like some other vascular endothelial growth factor inhibiting chemotherapeutic drugs may cause TTP-hemolytic uremic syndrome.

Hb S-β-thalassemia: molecular, hematological and clinical comparisons

Clinical and hematological features are presented for 261 patients with identified β-thalassemia (β-thal) mutations. Mutations causing Hb S [β6(A3)Glu→Val]-β(0)-thal were IVS-II-849 (A>G) in 44%, frameshift codon (FSC) 6 (-A) in 14%, Hb Monroe [β30(B12)Arg→Thr] in 14%, and IVS-II-1 (G>A) in 10%. Mutations causing Hb S-β(+)-thal with 14-25% Hb A (type III) were -29 (A>G) mutation in 60%, -88 (C>T) in 22% and the polyadenylation signal site (polyA) (T>C) mutation in 14%, and in Hb S-β(+)-thal with 1-7% Hb A (type I), all had the IVS-I-5 (G>C) mutation. Hematologically, only minor differences occurred between the four Hb S-β(0)-thal mutations, but among the three mutations causing Hb S-β(+)-thal type III, levels of Hb A(2), Hb F, hemoglobin (Hb), MCV and MCH were highest in the -88 and lowest in the polyA mutations. Clinically, Hb S-β(0)-thal and Hb S-β(+)-thal type I were generally severe, and Hb S-β(+)-thal type III disease with the -88 mutation was milder than that caused by the polyA mutation.

Sickle cell disease: old discoveries, new concepts, and future promise

The discovery of the molecular basis of sickle cell disease was an important landmark in molecular medicine. The modern tools of molecular and cellular biology have refined our understanding of its pathophysiology and facilitated the development of new therapies. In this review, we discuss some of the important advances in this field and the impediments that limit the impact of these advances.

Fatal Splenic Sequestration Crisis with Multiorgan Failure in an Adult Woman with Sickle Cell-Beta+ Thalassemia

Acute splenic sequestration crisis is a potentially fatal condition mostly seen in children with sickle cell anemia (HbSS) up to 6 years of age. Sickle cell-beta thalassemia has been associated with development of splenic sequestration crisis in rare reports. There have also been rare reports of the development of fatal acute splenic sequestration crisis together with severe multiorgan failure in adult patients with sickle cell-beta thalassemia. We describe a case of fatal splenic sequestration crisis together with multiorgan failure in a 34-year-old African-American woman with sickle cell-beta thalassemia syndrome.

Subclassification of HbS syndrome: is it necessary?

Sickle beta-thalassaemia (S beta-thalassaemia) is a condition, which results from coinheritance of a sickle cell gene and a beta-thalassaemia gene. The clinical phenotype depends on the type of beta-thalassaemia gene (beta+ or beta(o)). There are several similarities in clinical and haematological features, which sometimes pose a difficulty in correct diagnosis. A definitive diagnosis is required in order to initiate early supportive treatment in patients with homozygous sickle cell disease (SS disease) and to define the later clinical course. Forty-seven cases of haemoglobin sickle syndrome (HbS syndrome) were studied. The clinico-haematological features and high-performance liquid chromatography (HPLC) results from 17 patients with S beta-thalassaemia were compared with those of SS disease (10 patients). Splenomegaly was more commonly found in patients with S beta-thalassaemia. Among the haematological features, red blood cell counts and HbA2 levels were significantly higher in patients with S beta-thalassaemia, while red cell indices, such as MCV, MCH were significantly lower than those seen SS disease. MCHC, PCV total haemoglobin (Hb), HbS, A and HbF were similar in the two groups.

Intracellular Hemoglobin S Polymerization and the Clinical Severity of Sickle Cell Anemia

Recent work has enabled us to quantitate the four variables (2,3-DPG concentration, pHi, non-S hemoglobin composition, and O2 saturation) that modulate the equilibrium solubility (csat) of Hb S inside sickle erythrocytes (SS RBCs). Using measured values of mean corpuscular hemoglobin concentration (MCHC), 2,3-DPG concentration, and %Hb (F+A2), along with estimates of pHiand the Δcsat due to partial oxygenation of SS RBCs in the microcirculation, we calculated the mean polymer fraction (fp) in erythrocytes from 46 SS homozygotes. Values of fp derived from the conservation of mass equation ranged from 0.30 to 0.59. MCHC and %Hb F were major determinants of the magnitude of fp; 2,3-DPG concentration and pHialso contributed, but to a lesser extent. A clinical severity score (CSS) was assigned to each patient based on mean hospitalization rate. There was a weak, but statistically significant, negative correlation between fp and steady state hematocrit (P = .017), but none between fp and whole blood hemoglobin concentration (P = .218). Although there was no correlation between fp and mean number of hospitalization days per year, patients with the greatest number of admissions and hospitalization days were found only among those who had an fp > 0.45. All five patients who died during the follow-up period (median, 7 years; range, 3 to 10 years) had fp values ≥0.48. However, patients with few admissions, low hospitalization days, and long survivals occurred at all fp levels. These results suggest that the clinical course of homozygous SS disease cannot be predicted by mean fpcalculations, which assume a homogeneous distribution of the five variables that modulate intraerythrocytic polymerization. A heterogeneous distribution is more likely; so the amount of polymerized Hb S could vary considerably among cell populations. Factors such as membrane abnormalities and endothelial cell interactions may also contribute to clinical severity.

Intracellular Hemoglobin S Polymerization and the Clinical Severity of Sickle Cell Anemia

Recent work has enabled us to quantitate the four variables (2,3-DPG concentration, pHi, non-S hemoglobin composition, and O2 saturation) that modulate the equilibrium solubility (csat) of Hb S inside sickle erythrocytes (SS RBCs). Using measured values of mean corpuscular hemoglobin concentration (MCHC), 2,3-DPG concentration, and %Hb (F+A2), along with estimates of pHiand the Δcsat due to partial oxygenation of SS RBCs in the microcirculation, we calculated the mean polymer fraction (fp) in erythrocytes from 46 SS homozygotes. Values of fp derived from the conservation of mass equation ranged from 0.30 to 0.59. MCHC and %Hb F were major determinants of the magnitude of fp; 2,3-DPG concentration and pHialso contributed, but to a lesser extent. A clinical severity score (CSS) was assigned to each patient based on mean hospitalization rate. There was a weak, but statistically significant, negative correlation between fp and steady state hematocrit (P = .017), but none between fp and whole blood hemoglobin concentration (P = .218). Although there was no correlation between fp and mean number of hospitalization days per year, patients with the greatest number of admissions and hospitalization days were found only among those who had an fp > 0.45. All five patients who died during the follow-up period (median, 7 years; range, 3 to 10 years) had fp values ≥0.48. However, patients with few admissions, low hospitalization days, and long survivals occurred at all fp levels. These results suggest that the clinical course of homozygous SS disease cannot be predicted by mean fpcalculations, which assume a homogeneous distribution of the five variables that modulate intraerythrocytic polymerization. A heterogeneous distribution is more likely; so the amount of polymerized Hb S could vary considerably among cell populations. Factors such as membrane abnormalities and endothelial cell interactions may also contribute to clinical severity.

Fatal bone marrow embolism in a patient with sickle cell beta + thalassaemia

Sickle cell beta + thalassaemia is regarded as the mildest of the sickle cell haemoglobinopathy syndromes with a benign natural course. In contrast to sickle cell disease, severe life threatening complications are not usually associated with this genotype. A case of a 30 year old West Indian man who, previously asymptomatic for 10 years, sustained a fatal pulmonary bone marrow embolism, is reported. This case report illustrates that serious, even fatal, complications may occur in patients with this 'benign' condition and bone marrow embolism should be included in the differential diagnosis of acute crisis in these patients.

Laboratory diagnosis of hemoglobinopathies

Diagnostic tests for most common hemoglobinopathies and recent advances in structural analysis of variant hemoglobins are reviewed. Routine and newly introduced methods that apply to the diagnosis of sickle cell anemia, thalassemia and the hemoglobin E disorders are presented. A brief description of the clinical course for each of these disorders is given, and potential pitfalls in diagnosis are discussed. Application of high-performance liquid chromatography and various mass spectrometric techniques (electrospray ionization mass spectrometry, liquid secondary ion mass spectrometry, and tandem mass spectrometry) for evaluation of hemoglobinopathy is presented.

A comparison of sickle cell syndromes in northern Greece

Haematological and clinical characteristics have been examined in 30 patients with homozygous sickle cell (SS) disease, 28 with sickle cell-beta zero thalassaemia, and 21 with sickle cell-beta+ thalassaemia. The latter could be divided into three groups on their molecular basis and HbA levels, four subjects with an IVS-2 nt 745 mutation having 3-6% HbA (designated S beta+ thalassaemia type I), 14 subjects with an IVS-1 nt 110 mutation having 8-15% HbA (designated S beta+ thalassaemia type II), and three subjects with an IVS-1 nt 6 mutation having 20-25% HbA (designated S beta+ thalassaemia type III). Comparisons were conducted between SS disease, S beta zero thalassaemia, and S beta+ thalassaemia type II. Compared to SS disease, both thalassaemia syndromes had higher HbA2 levels and red cell counts and lower mean cell haemoglobin content (MCHC), mean cell volume (MCV) and MCH, and S beta zero thalassaemia had higher HbF and reticulocyte counts. Compared to S beta zero thalassaemia, S beta+ thalassaemia had a higher haemoglobin and MCHC. Clinically, persistence of splenomegaly was more common in S beta zero and S beta+ thalassaemia type II compared to SS disease. Few significant differences occurred between SS disease, S beta zero and S beta+ thalassaemia type II in Northern Greece suggesting that the 8-15% HbA in the latter condition was insufficient to modify the clinical course.

Intracellular polymerization. Disease severity and therapeutic predictions

The extent of intracellular polymerization of hemoglobin S, leading to loss of erythrocyte deformability and eventual morphological sickling, is primarily determined by oxygen saturation and intracellular hemoglobin concentration and composition. Epidemiological analysis of sickle cell disease severity among the sickle syndromes and studies of the biophysics of intracellular polymerization were used to estimate the potential clinical benefit of various therapeutic strategies. These strategies include those designed to increase deoxyhemoglobin S solubility; to increase erythrocyte volume or water content, thereby reducing the intracellular hemoglobin concentration; or, most recently, to decrease the proportion of hemoglobin S by increasing the amount of non-S hemoglobin. Increasing levels of hemoglobin F is of particular interest due to its "sparing" effect in inhibiting polymerization, the well-characterized epidemiological associations of high levels of hemoglobin F with reduced disease severity, and recent studies of drug-induced increases in hemoglobin F. Our analyses of equilibrium polymer formation at physiological oxygen saturation values suggest that small decreases in polymer formation at intermediate levels of hemoglobin F may give rise to a small decrease in anemia (as associated with homozygous alpha-thalassemia coexistent with sickle cell anemia), but that greater reductions in polymer formation may be necessary to effect a significant improvement in disease severity. Current studies of hydroxyurea-induced increases of hemoglobin F give cautious optimism that therapeutically useful levels may be attainable.

Effect of polymerization tendency on haematological, rheological and clinical parameters in sickle cell anaemia

The polymerization tendency of sickle haemoglobin was estimated as a function of oxygen saturation in 30 patients with homozygous sickle cell anaemia. The deformability of their erythrocytes was also measured, by initial-flow-rate filtration at 37 degrees C through pores of 5 microns diameter, and clinical severity was assessed using a visual analogue scale. By means of partial correlation analysis, it was found that correlations between haematological, rheological, and clinical parameters in sickle cell anaemia could be explained on the basis of an association of each variable with polymerization tendency. Patients with the greatest tendency to form polymer had the least deformable erythrocytes and perceived their disease to be more severe as judged by the visual analogue scale. Polymer formation also appeared to be a determinant of the number of dense cells which, in turn, determine haemolytic rate and erythrocyte deformability.

Sickle cell-hereditary persistence of fetal haemoglobin and its differentiation from other sickle cell syndromes

Some haematological indices were compared in 13 subjects with sickle cell-hereditary persistence of fetal haemoglobin (S-HPFH) and in 10 patients with homozygous sickle cell (SS) disease and four patients with sickle cell-beta zero thalassaemia, all with fetal haemoglobin (HbF) levels of 20% or above. Sickle cell-beta zero thalassaemia could be differentiated by a high HbA2 level. S-HPFH could be distinguished from SS disease with a high HbF level by red cell count, HbF level, reticulocyte count, total haemoglobin and total bilirubin level in decreasing power of discrimination.

Clinical and molecular correlations in the sickle/beta+-thalassemia syndrome

Sickle/beta thalassemia is a sickling disorder of varying severity which results from compound heterozygosity for sickle cell trait and beta-thalassemia trait. Clinical and genetic studies have shown an inverse correlation between the level of hemoglobin A and the severity of the disease. It has been suggested that the level of hemoglobin A may be a function of the severity of the beta-thalassemia defect. In this study, we use molecular biological techniques to test this hypothesis. We show that the interaction of the mildest of the beta+-thalassemia genes with the sickle gene results in a high level of hemoglobin A. However, the interaction in this case resulted in a severe sickling disorder in the absence of significant anemia. We hypothesize that a mild beta+-thalassemia gene may have two opposite effects on the clinical course of sickle/beta+ thalassemia: (1) A high level of hemoglobin A which probably confers a favorable antisickling effect and (2) decreased hemolysis leading to increased numbers of total circulating red cells, thereby increasing the blood viscosity and the propensity for sickling. The inheritance of heterozygous alpha thalassemia 2 in conjunction with the mild beta+-thalassemia gene and sickle gene in this patient may have further enhanced the latter effect and resulted in a severe sickling disorder.

Haematological change in sickle cell-haemoglobin C disease and in sickle cell-beta thalassaemia: a cohort study from birth

The haematological changes in early years following neonatal diagnosis have been observed in representative groups of children with sickle cell-haemoglobin C (SC) disease, sickle cell-beta(+) thalassaemia, and in sickle cell-beta(0) thalassaemia. Most haematological indices in SC disease were intermediate between previously published values in SS disease and in AA controls, generally being closer to values in normal children. Exceptions were microcytosis which may be genetically determined and a striking elevation of mean cell haemoglobin concentration from age 2 months to 4 years. The combination of a raised MCHC and a lowered MCV is unusual and may be characteristic of SC disease. Features in sickle cell-beta thalassaemia generally differed according to the type of beta thalassaemia gene. Sickle cell-beta(0) thalassaemia had lower levels of haemoglobin, MCHC, red cell count, MCV, and higher reticulocytes, most differences being significant before 1 year. No differences between S beta(0) thalassaemia and S beta(+) thalassaemia were apparent in HbF levels (which resembled those in SS disease) or in HbA2 levels (which exceeded those in SS disease by 1 year of age).

Interaction between HBS-beta-o-thalassemia and alpha-thalassemia

We have defined the clinical and laboratory characteristics of a group of patients with HbS-beta o-thalassemia plus alpha-thalassemia, by analysis of erythrocyte indices, hemoglobin A2 and F levels, globin biosynthesis studies and alpha-globin gene mapping. Patients with HbS-beta o + alpha-thalassemia closely resembled individuals with HbS-beta o-thalassemia except for balanced globin synthesis ratios and a lower HbF level. The frequency of painful crises, leg ulceration, aseptic necrosis of bone and acute chest syndrome was similar in HbS-beta o + alpha-thalassemia patients and controls with sickle cell anemia (HbSS), HbSS-alpha-thalassemia and HbS-beta o-thalassemia. These findings are consistent with previous work which failed to show a reduction in the vaso-occlusive severity of sickle cell disease by the coexistence of alpha-thalassemia.

Sickle cell disease in Britain

Sickel cell disease is common in urban areas of Britain and it is estimated that in London alone there are nearly 2000 patients. One hundred and eighty four patients with sickle cell disease are known to the Central Middlesex Hospital, and 155 of those attend the sickle cell clinic regularly. The commonest cause for admission to hospital is acute painful or vaso-occlusive crisis, which accounts for 80% of all acute admissions; 12% of admissions are for acute chest syndrome. Comparison of clinical features in Brent and in Jamaica shows that the Brent patients with homozygous sickle cell anaemia are admitted with painful crises more frequently than Jamaican patients. However, the frequency of admissions for chest syndrome and priapism, and the incidence of splenomegaly are similar. Leg ulcers are uncommon in Brent. Patients with sickle cell haemoglobin C disease appeared more severely affected in Jamaica than in Brent. During the past two years 3165 newborn babies have been screened for sickle cell disease at the Central Middlesex Hospital: five babies with homozygous sickle cell anaemia and three babies with sickle cell haemoglobin C disease were detected. The overall incidence of sickle cell trait was 3.2% and of haemoglobin C trait 0.8%. A significant number of babies with sickle cell disease are born in London every year. It is essential that such babies are detected at birth and offered prophylaxis against pneumococcal infection, which is one of the major causes of infant mortality. Sickle cell disease is becoming an important blood disease in Britain and firm guidelines for the management of acute and chronic complications are required.

Bone infarction in children with sickle cell disease: early diagnosis and differentiation from osteomyelitis

An early differential diagnosis between bone infarction and osteomyelitis in sickle cell patients is practically impossible using routine laboratory methods. Twenty radioisotope studies in sickle cell patients during vaso-occlusive crises, were analyzed. A three stage process can be described. In the first stage a decreased uptake can be demonstrated by Tc 99m methylene diphosphonate (MDP) bone scanning. In osteomyelitis, an increased uptake area is usually seen at this early stage, corresponding to increased uptake in Ga-67 citrate scanning. At the second stage, approximately a week later, normal uptake can be seen. Two to four weeks later an area of increased uptake is recorded that corresponds to the healing process, stage three. We recommend therefore Tc 99m MDP bone scanning in the early stages if clinical signs and symptoms suggest a vaso occlusive crisis or osteomyelitis in a sickle cell patient. This study can be followed by a Ga-67 citrate scintigraphy in doubtful cases. Later studies should be used for the assessment of the healing process. Two illustrative case reports are included.

Sickle cell beta-thalassaemia compared with sickle cell anaemia in Algeria

Clinical, haematological and biochemical features in 42 subjects with S-beta thalassaemia (31 subjects with S-beta thalassaemia and 11 subjects with S-beta+ thalassaemia); and in 42 with homozygous sickle cell disease were compared. Persistent splenomegaly was more common and painful crises less common in the S-beta thalassaemia group. Total Hb was higher and reticulocyte count lower in S-beta+ thalassaemia than in S-beta thalassaemia or SS disease. Microcytosis was marked in the S-beta thalassaemia group while the MCV was normal in sickle cell anaemia. Hb F was significantly higher in the S-beta thalassaemia group, without any influence on the severity of the disease. Many features suggest that sickle cell thalassaemia is more severe in Algeria than in Negro subjects and similar to the disease in Italian patients.

The interaction of alpha-thalassemia and homozygous sickle-cell disease

Patients with homozygous sickle-cell disease may be homozygous for alpha-thalassemia 2 (alpha-/alpha-), may be heterozygous for alpha-thalassemia 2 (alpha-/alpha alpha), or may have a normal alpha-globin-gene complement (alpha alpha/alpha alpha). We compared the clinical and hematologic features of 44 patients who had sickle-cell disease and homozygous alpha-thalassemia 2 with those of controls with the two hematologic conditions. The patients with homozygous alpha-thalassemia 2 had significantly higher red-cell counts and levels of hemoglobin and hemoglobin A2, as well as significantly lower hemoglobin F, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, mean corpuscular volume, reticulocyte counts, irreversibly-sickled cell counts, and serum total bilirubin levels, than those with a normal alpha-globin-gene complement. Heterozygotes (alpha-/alpha alpha) had intermediate values. In the group with homozygous alpha-thalassemia 2, fewer patients had episodes of acute chest syndrome and chronic leg ulceration and more patients had splenomegaly, as compared with patients in other two subgroups. These data confirm previous suggestions that alpha-thalassemia inhibits in vivo sickling in homozygous sickle-cell disease and may be an important genetic determinant of its hematologic severity.

An update on electrophoretic and chromatographic methods in the diagnosis of hemoglobinopathies

This review primarily deals with methods for separations of hemoglobins. An introduction considers electrophoretic methods as well as those involving isoelectric focusing and chromatography. The main advantages or disadvantages of each procedure are discussed after each technical description. The chromatographic methods are mainly limited to those used in clinical biochemistry. The second section treats the main diagnostic problems typically met with in the field of the hemoglobinopathies and deals successively with the diagnosis of hemoglobinopathies in the adult and the newborn. Numerous variants have been described in the adult, and among them Hb-S and Hb-C variants are the most frequent. Unstable or high oxygen affinity variants of hemoglobin are also considered. Finally, a new strategy for diagnosis is proposed. A special section is devoted to the diagnosis of thalassemia syndromes. The prenatal diagnosis of hemoglobinopathies is also discussed in some detail with a view to preventing the birth of homozygous children. This update ends with a chapter on the interest of the assay of hemoglobins A1c in the pathology of diabetes mellitus.

Sickle cell haemoglobinopathies in England

Ninety-six Birmingham children with sickle cell disease were studied prospectively between 1969 and 1979. Thirty-five were homozygotes for HbS (SS), 12 had sickle thalassaemia (S thal), and 23 were double heterozygotes for HbS and C (SC). Twenty-six whose family studies were incomplete were classified as SS or S thal although most were thought to be SS. The average length of follow-up was 5.1 years. Four SS children and 1 SC child died, the annual mortality rates being 1.3% for SS and presumed SS, 0% for S thal, and 0.9% for SC children. The incidence of pulmonary illnesses and anaemic crises was greater than reported from Jamaica, while leg ulceration described there and in New York was not observed in Birmingham. Severe infections were less common than in the series reported from New York and no case of salmonella osteomyelitis was observed in Birmingham. In general the S thal and SC children had milder illnesses than the SS, and the SS children often showed impairment of growth and sexual maturation.

Observations on the natural history of dactylitis in homozygous sickle cell disease

The incidence of the hand-foot syndrome (dactylitis) has been studied in a group of 233 children with homozygous sickle cell (SS) disease followed prospectively from birth. Dactylitis affected 45% of the children by the age of 2 years, with most cases occurring before this age. Episodes were significantly more common during colder months of the year, similar to the seasonal relationship previously noted in painful crises. Comparison of hematologic indices at age 6 months in patients with and without development of dactylitis indicated a lower fetal hemoglobin and higher reticulocyte counts in affected patients. The occurrence of dactylitis in combination with low fetal hemoglobin may serve to identify high-risk patients with SS disease.

Sickle cell anemia as a rheologic disease

Sickle cell anemia represents an aberration of blood rheology due to a loss of normal red cell deformability. The characteristically low hematocrit compensates for the stiffness of the sickle cells, leaving the patient with approximately normal whole blood viscosity. However, the microvascular flow of sickle cell blood is constantly jeopardized by hemoglobin gellation due to hypoxemia. The cells containing the highest concentration of hemoglobin S are the most viscous and are at the greatest risk for abrupt sickling. Successful treatment of this disease will require interruption of the basic pathogenetic mechanisms and preservation of normal blood rheology.

Observations on the epidemiology of sickle cell disease

The four common genotypes of sickle cell disease in Jamaica are homozygous sickle cell (SS) disease, sickle cell-haemoglobin C (SC) disease, sickle cell-B+ thalassemia, and sickle cell-BO thalassaemia with respective incidence at birth of 3.2, 2.0. 0.34, and 0.16 per 1000 live births. Haematological indices, clinical features, and over-all prognosis vary between these genotypes and also between patients within individual genotypes. Although symptomatic selection has tended to emphasize more severely affected patients, this wide variation of clinical and haematological severity is especially apparent in SS disease. Factors contributing to this variability in SS disease include the persistence of foetal haemoglobin, the association with alpha thalassemia, and the interaction with environmental factors of which socioeconomic status is the most obvious. Further elucidation of factors determining the severity of SS disease will increase understanding of the pathogenetic mechanisms in the disease and may also identify new possibilities for therapeutic intervention.

Clinical, hematological and genetic features of sickle-cell anemia and sickle cell-beta thalassemia in a Brazilian population

Clinical, hematological and genetic studies were carried out on 40 patients with symptomatic sickle-cell disease, selected on the basis of a predominant HbS fraction and absence of other abnormal hemoglobin variants. Family studies showed they included 26 homozygotes for the sickle-cell gene (SS) and 14 double heterozygotes for both the sickle-cell and the (0)beta-thalassemia genes ((S)(0)beta-thalassemia). Comparison of the two groups revealed the more common occurrence of splenomegaly, lower MCV and mCH, and higher HbA2 in (S)(0)beta-thalassemia. Total hemoglobin was slightly lower in SS disease but the difference was not significant. Fetal hemoglobin (HbF) was moderately elevated to similar levels in both groups. These results suggest a high incidence of S beta (0)-thalassemia in certain Brazilian mixed populations and confirm the severity of the double heterozygous state. The distinction between the two disorders is often difficult, but can be made on the basis of the hematological data taken together with family studies.

Hematological and clinical features of sickle cell diseases: a review

The differentiation, hematologic features and clinical manifestations of patients with the various sickling disorders are reviewed. The deficiencies in our current knowledge about the spectrum of the clinical course of patients with these conditions is discussed. The interaction of alpha thalassemia with sickle cell anemia and its possible effect upon the severity of the disease is summarized. The apparent milder disease in certain groups of patients with sickle cell anemia in whom there is an associated elevation of hemoglobin F is contrasted with the controversy surrounding the effects of hemoglobin F levels in the patients of African origin.