Effects of hydroxyurea in a population of Brazilian patients with sickle cell anemia

Fetal hemoglobin (HbF) inhibits the polymerization of sickle hemoglobin, modulating the clinical features of sickle cell anemia (SCA). Hydroxyurea (HU) therapy can increase the HbF level, although its production can be influenced by genetic determinants. Twenty-two Brazilian SCA patients were evaluated over 5 years before and after HU use. We analyzed (1) betaS haplotype; (2) patient characteristics; and (3) toxicity. No differences between age, sex, and HU response were observed. We found 40.9% of homozygous for Bantu haplotype, and, in contrasting to other trials, we observed HbF level increase in this group (3.84-9.08 g/dL, P=0.003). Adverse effects were rare. Labyrinthitis was observed in 2 (9.10%) patients after HU use, although this complication had not been described before.     

Molecular characteristics of pediatric patients with sickle cell anemia and stroke

Cerebrovascular accidents (CVA) are serious complications of sickle cell anemia (SS) in children. Factors that predispose children to this complication are not well established. In an effort to elucidate the risk factors associated with CVA in SS, we have determined the alpha-globin genotype and the beta(S) haplotype of children with this complication. Among 700 children with SS followed at Children's Hospital of Michigan, 41 (6%) are on chronic transfusions because of stroke due to cerebral infarction. The mean age of patients with CVA at the time of stroke was 5.6 +/- 3.2 years (mean +/- SD). The male/female ratio was 2/3. Only 8 of 41 patients (19.5%) had one alpha-gene deletion, compared to the reported prevalence of 30% in African-Americans. None of the patients had two alpha-gene deletions, and two (5%) had five alpha-genes. These findings are different than those in our adult patients with SS, where the prevalence of -alpha/-alpha and alphaalphaalpha/alphaalpha is 4% and <2%, respectively. Ten different beta(S)-haplotypes were detected in the patients studied. The majority of the patients (31%) were doubly heterozygous for the Ben/CAR haplotypes followed by Ben/Ben, Ben/Sen, and CAR/CAR haplotypes, respectively. The prevalence of these haplotypes, with the exception of the CAR/CAR haplotype, was higher in females than males. All the patients with CAR/CAR haplotype were males, had four alpha-genes, and ranked third in prevalence. Three patients were heterozygous for the Cameron haplotype. The Cameron and atypical haplotypes were more prevalent than reported in patients with SS at large. The data suggest that CVA in children seems to occur more frequently in females and in patients with certain beta(S) haplotype. alpha-Gene deletion seems to offer a protective effect against this complication. Neonates with four or more alpha-genes whose beta(S) haplotype is Ben/CAR, atypical, or CAR/CAR seem to be at a higher risk for CAV than other patients. A prospective study on a larger group of patients with or without CVA may clarify this issue.     

Hemoglobin Lepore Hollandia in India

Introduction: Hb Lepore is a structurally abnormal hemoglobin in which the abnormal globin chain is a hybrid or fused δβ globin chain. In the heterozygous condition, Hb Lepore produces the phenotype of heterozygous β thalassemia with slightly raised HbF levels. Method: Using a combination of HPLC and DNA analysis, we have identified eight individuals with Hb Lepore Hollandia from three families including seven heterozygotes and one compound heterozygote with β thalassemia who presented with a severe clinical phenotype. Results: All the heterozygotes showed elevated levels of HbF with a mean of 3.2%. Hb Lepore Hollandia genes were associated with a single β globin cluster haplotype [‐ ‐ ‐ ‐ ‐ ‐ +] indicating a common origin. Conclusion: Hemoglobin Lepore Hollandia is a relatively uncommon variant in the Indian population and can be identified using a combination of chromatographic, electrophoretic, and molecular analysis.     

Sickle cell anemia and trait in southern India: further studies.

Population surveys and family studies among 568 members of nine ethnic groups in southern India identified 15 homozygotes for sickle hemoglobin (HbS)who had mild clinical and hematological manifestations with high levels of fetal hemoglobin (mean=20%, range 8-36%) in a heterogeneous red cell distribution. In one family, the heterozygous mother had a hemoglobin pattern consistent with a form of the heterocellular hereditary persistence of fetal hemoglobin. Sickle cell trait was found in 153(27%) of those studied. Chromatographic quantitation of the hemoglobin fractions in these heterozygotes showed a trimodal distribution of the proportion of HB Sexplicable by a genetic model postulating the presence of genotypes with two (-alpha/-alpha), three (-alpha/alpha alpha) and four (alpha alpha/alpha alpha) active alpha-globin genes. Globin synthesis studies in four heterozygotes believed to have two active alpha-globin genes demonstrated an alpha/non-alpha total activity ratio (0.57) consistent with this model.     

Concordant fetal hemoglobin response to hydroxyurea in siblings with sickle cell disease

Fetal hemoglobin (HbF) level and the HbF responses to hydroxyurea (HU) vary among patients with sickle cell disease and are, at least in part, genetically regulated. We hypothesized that siblings with sickle cell disease are likely to share the same parental beta-like globin gene clusters with their cis-acting regulatory sequences and therefore, if regulation of this response is linked to the beta-globin gene cluster, might have concordant HbF responses to HU. Accordingly, we studied 26 families (30 sib pairings), 20 with sickle cell anemia (three families had three siblings) and 6 families with HbS-beta-thalassemia (one family had three siblings, and one family consisted of monozygotic twins), to see if siblings with sickle cell disease had discordant or concordant changes in HbF during HU treatment. Intraclass correlation coefficients (r) showed a high, positive correlation between sibs for HbF levels before and during HU treatment and a concordant change in HbF response from baseline to treatment-associated levels. Changes in mean corpuscular volume (MCV) paralleled HbF levels, while the expected correlations between treatment-associated fall in leukocyte count and increase in MCV were also present. Our results provide additional evidence that some elements that regulate HbF expression are linked to the beta-globin gene cluster.     

High incidence of autoimmune alterations in chronic myeloid leukemia patients treated with interferon-alpha

Interferon-alpha is the frontline therapy of the majority of chronic myeloid leukemia (CML) patients who are not eligible for bone marrow transplantation. Many patients are treated for long periods, and there is concern about the long-term immune effects of its use. Autoimmune disorders in patients treated with IFN-alpha may be related to the direct immunomodulating properties of IFN or may be linked to a possible toxic effect in target organs, triggering autoimmunity. On the other hand, the immune effects of IFN may play a role in its therapeutic actions. The aims of our study were to assess the incidence of autoimmune phenomena in these patients, and to measure the possible association between the generation of autoimmune phenomena and the antileukemic effect of IFN alpha. Therefore, 46 patients with Ph1(+) CML in the first chronic phase were studied for the appearance of immune complications, their connection to IFN dose, time of appearance, and the possible association with the response to treatment. Autoimmune abnormalities have been found in 28% of our patients. Moreover, a significant association was found between autoimmune alterations and female sex (P = 0.02, OR 4.5, 95% CI 1.13-17.9) and a longer treatment time (1.6 vs. 4.1 years) (P = 0.02; OR 1.01, 95% CI 1-1.02). The Kaplan-Meier estimated probability of obtaining a cytogenetic response was significantly higher in patients who developed autoimmune alterations (P = 0.049), and this difference was also evident in Cox's analysis when controlling with other potentially confounding variables (P = 0.078). We conclude that CML patients treated with IFN alpha have a high incidence of autoimmune phenomenon.     

Relationship of foetal haemoglobin levels and beta s haplotypes in homozygous sickle cell disease.

The foetal haemoglobin (HbF) levels and the haplotypes of beta s chromosomes in sickle cell anaemia patients in Nigeria were evaluated. The mean HbF level was 5.9 +/- 3.8% with a range of 0.9-16.7%. 80% of the patients had HbF values below 8% and 94% had HbF levels below 10%. No significant difference in haematological parameters was seen between those with less than 2% HbF and those with greater than 8% HbF. The presence (+) or absence (-) of eight restriction endonuclease enzyme sites within the beta s globin gene cluster (haplotype) on chromosome 11 were mapped. The common haplotype (- - - - + + - +) in 97% of the chromosomes examined closely correlates with the low levels of foetal haemoglobin generally observed in sickle cell patients in the same population.     

Beta S gene in Sicily is in linkage disequilibrium with the Benin haplotype: implications for gene flow

Hemoglobin beta-like gene cluster haplotypes defined by restriction enzyme polymorphic sites are useful in determining the origin of the beta S gene found in several human populations. We present here evidence that the beta S gene found among Sicilians is associated with the same haplotype observed among sickle cell anemia patients from Central West Africa. In addition, this haplotype is either nonexistent or very rare among normal Sicilian individuals. We conclude that the beta S gene was introduced to Sicily from North Africa and that the gene flow originated in Central West Africa and traveled north through historically well-defined trans-Saharan commercial routes.     

Acute chest syndrome is associated with single nucleotide polymorphism‐defined beta globin cluster haplotype in children with sickle cell anaemia

Genetic diversity at the human β‐globin locus has been implicated as a modifier of sickle cell anaemia (SCA) severity. However, haplotypes defined by restriction fragment length polymorphism sites across the β‐globin locus have not been consistently associated with clinical phenotypes. To define the genetic structure at the β‐globin locus more thoroughly, we performed high‐density single nucleotide polymorphism (SNP) mapping in 820 children who were homozygous for the sickle cell mutation (HbSS). Genotyping results revealed very high linkage disequilibrium across a large region spanning the locus control region and the HBB (β‐globin gene) cluster. We identified three predominant haplotypes accounting for 96% of the β^S‐carrying chromosomes in this population that could be distinguished using a minimal set of common SNPs. Consistent with previous studies, fetal haemoglobin level was significantly associated with β^S‐haplotypes. After controlling for covariates, an association was detected between haplotype and rate of hospitalization for acute chest syndrome (ACS) (incidence rate ratio 0·51, 95% confidence interval 0·29–0·89) but not incidence rate of vaso‐occlusive pain or presence of silent cerebral infarct (SCI). Our results suggest that these SNP‐defined β^S‐haplotypes may be associated with ACS, but not pain or SCI in a study population of children with SCA.     

Sickle cell anemia associated with alpha-thalassemia in Malaysian Indians

The Indian rubber estate workers in Negri Sembilan, Malaysia, who originated from Orissa in India were found to have a high frequency of Hb S (Joishy SK, Hassan K: Clin Res 28:280, 1980). Unlike the usually severe clinical picture of sickle cell anemia seen in African and American blacks, the clinical picture of the disease in this population was mild and many have reached old age. We studied the leukocyte DNA of 12 patients with sickle cell anemia, ranging in age from 4 to 61 years and 30 sickle cell trait carriers, ranging in age from 7 to 63 years, for the presence of alpha-globin gene deletions by gene mapping according to Southern (Southern EM: J Mol Biol 98:503, 1975), using alpha- and zeta-globin gene probes obtained by nick translation of the alpha- and zeta-globin genes cloned into plasmid. All 12 sickle cell anemia patients were found to have alpha-thalassemia2 (alpha-thal2), either in the homozygous or heterozygous condition. Of the Hb S trait carriers, six did not have alpha-thal2 or alpha-thal1 and 24 had alpha-thal2 (15 heterozygous, 9 homozygous). Seven of these Hb S trait carriers with alpha-thal2 had an additional gene abnormality. Five of them had a fast-moving Eco RI fragment 5.6 kb long that hybridized with zeta-specific probe but not with alpha-specific probe. An unusual DNA pattern of a different type was further found in the other two. Bgl II restriction analysis showed that the alpha-thal2 was mostly of the rightward deletion alpha-thal1 genotype. None of the sickle cell anemia patients and Hb S trait carriers had deletion type alpha-thal1. The sickle cell anemia patients had very high levels of Hb F and low levels of Hb A2. The Hb S trait carriers with alpha-thal2 had relatively low levels of Hb S.     

Molecular analysis of the β-globin gene cluster haplotypes in a Sudanese population with sickle cell anaemia

Introduction: Sudan has a multiethnic population with a high frequency of Hb S, but little is known about the β^S haplotypes in this population. Methods: Blood samples from Sudanese Hb SS individuals were taken at two locations. Family history, age, ethnicity and clinical symptoms were recorded for each subject. Hb S was investigated using cellulose acetate electrophoresis (CAE) and cation exchange–high performance liquid chromatography. Dried blood samples from 93 individuals were used for β^S haplotype identification based on restriction fragment length polymorphism analysis for seven restriction sites. Results: Haplotypes could be assigned unequivocally to 143 chromosomes. Four of the five typical β^S‐globin haplotypes were identified. The most frequent was the Cameroon (35.0%), followed by the Benin (29.4%), the Senegal (18.2%) and the Bantu (2.8%). The Indian‐Arab haplotype was not observed. Three atypical haplotypes were identified in 17 patients, occurring at a combined frequency of 14.6%. One of these, found at the high frequency of 11.8%, possibly represented a new Sudan haplotype. Conclusion: β^S Haplotyes were demonstrated successfully from dried blood samples. A new haplotype is apparent in Sudan, in addition to the four African haplotypes.     

High frequency of deletional alpha-thalassemia in beta-thalassemia trait: implications for genetic counseling

Thalassemias are a group of genetic hemolytic disorders with varying phenotypes. In this study, the frequency of alpha globin gene deletions was studied in the beta-thalassemia trait, the mildest form of the disorder. Eleven out of 33 (33%) individuals were positive for alpha(-3.7 kb) deletions. None of the subjects was positive for the Southeast Asian deletion. Such a high frequency for alpha deletions has not been reported earlier in thalassemia minor. Hematological parameters are compared, and implications of this finding for genetic counseling are discussed.     

Effect of LMO2 protein expression on survival in chronic myeloid leukemia patients treated with imatinib mesylate

Abstract

LIM domain only-2 (LMO2) is an important regulator of hematopoietic stem cell development. LMO2 protein is expressed in all three hematopoietic lineages precursors of the hematopoietic system, and its expression has been shown to decrease gradually during differentiation. Chronic myeloid leukemia (CML) is a malignant clonal myeloproliferative disorder in which the terminal differentiation is not altered until the appearance of an accelerated or blast phase. We examined whether LMO2 protein expression can predict outcome CML patients undergoing tyrosine kinase inhibitor therapy, imatinib mesylate (IM). Immunohistochemistry on bone marrow biopsy material for LMO2 protein was performed in 47 CML patients. We report that the LMO2 protein expression is correlated with improved hematologic remission and overall survival in the CML patients treated with IM. The immunohistologic analysis of LMO2 protein expression may become a predictive factor for anticipating the treatment responses of CML patients.     

Sickle cell anemia as a syndrome: a review of diagnostic features.

Sickle cell (SS) disease is a complex of various genetic conditions. In some, homozygosity for the beta S gene may be present alone or in combination with the heterozygous or homozygous alpha-thalassemia-2 condition. Such combinations might ameliorate the clinical and hematological condition of the patient. The same may be true for the high levels of Hb F and F-cells observed in many Hb S homozygotes. Howeever, the chemical heterogeneity of Hb F appears not to be related to the clinical status of the Hb S homozygote. Combinations of a Hb S heterozygosity with a heterozygosity for a Hb D-type of variant, for either one of two types of beta-thalassemia, two types of alpha beta- thalassemia, and five types of HPFH are discussed, and data are compared with those obtained for Hb S homozygotes. The use of advanced laboratory procedures and family studies is often necessary for an accurate diagnosis.     

甲磺酸伊马替尼治疗慢性粒细胞白血病附加异常Ph阳性克隆的预后意义

目的探讨甲磺酸伊马替尼（伊马替尼）治疗后慢性粒细胞白血病（CML）具有附加异常的Ph阳性克隆的演变及其预后意义。方法收集37例CML加速期和急变期患者的骨髓标本培养24h,G显带进行核型分析。结果伊马替尼治疗前患者的附加染色体种类主要有双Ph、＋8、i（17q）等,其次还有-Y、除i（17q）外17号的异常、inv（3q）等,以及少见的易位和其他异常。伊马替尼治疗后具有附加异常的Ph阳性克隆比例发生扩增、基本不变、比例下降、完全消失等4种形式的演变。24例加速期患者中有2例获得完全细胞遗传学缓解（CCyR）,13例急变期患者中2例获CCyR。附加异常克隆扩增／不变组的中位生存时间和无疾病进展时间显著短于比例下降／完全消失组（P〈0．05）。结论有附加染色体异常的Ph阳性CML患者伊马替尼治疗后附加异常克隆比例可以下降甚至完全消失,获得CCyR,并伴生存期延长。     

Hemoglobin SE disease: a concise review

An infant with Hb SE disease is reported. He was clinically well. Review of the literature shows that patients aged 18 and younger are usually well. On the other hand, more than half of those aged 20 and older developed sickling-related complications, including potentially life-threatening acute chest syndrome. These patients have 60-65% Hb S, similar to the percent Hb S in patients with Hb S/beta(+)-thalassemia. Their hematological features and clinical course appear to parallel those of Hb S/beta(+)-thalassemia. Patients have variable levels of anemia, and some develop clinical complications. With population migrations and increasing racial intermarriages, Hb SE disease is expected to be encountered more often around the globe. Patients with Hb SE disease should be followed and managed in a similar fashion as those with Hb S/beta(+)-thalassemia, and treated appropriately when they develop sickling-related symptoms and complications.     

UGT1A1 polymorphism outweighs the modest effect of deletional (-3.7 kb) alpha-thalassemia on cholelithogenesis in sickle cell anemia

Enhanced erythrocyte destruction in sickle cell anemia results in chronic hyperbilirubinemia. Only a subset of patients develop cholelithiasis. UGT1A1 promoter polymorphism is associated both with unconjugated bilirubin level and elevated risk for cholelithiasis in such subset. Here, we investigated the role of alpha-thalassemia, yet another genetic factor that modulates hemolysis, in conferring protection from cholelithiasis. We show that, although alpha-thalassemia is associated with modest reduction in hemolysis and unconjugated bilirubin level, UGT1A1 polymorphism outweighs its effect on cholethiogenesis in sickle cell anemia patients.     

The effect of Hb F and alpha-thalassemia on the red cell indices in sickle cell anemia

This study examines the effect of different levels of fetal hemoglobin (Hb F) and the presence or absence of genes for alpha-thalassemia on the red cell indices and degree of anemia among 102 patients with homozygous sickle cell disease (S/S) between the ages of 15 and 62 years. Patients were divided into those with an average Hb F of less than 10 gm/L ("low" Hb F group) and those with greater than 10 gm/L ("high" Hb F group). alpha-Thalassemia was assessed by restriction enzyme analysis of DNA by the Southern blotting technique. Homozygosity for the beta(s) gene was confirmed by restriction enzyme analysis of DNA using the enzyme Mst II. There were 51 patients with four alpha-globin genes, 28 of whom had "high" and 23 "low" Hb F levels. Fifty-one patients had alpha-thalassemia, 38 of whom were heterozygous and 13 homozygous for the 3.7 kb alpha-thalassemia deletion. Nine had "high" and 31 had "low" Hb F. Irrespective of alpha-globin genotype, patients in the high Hb F group had a higher mean Hb, Hct, MCV, and MCH than those in the low HB F group. In patients without alpha-thalassemia Hb F was positively correlated with MCV and MCH (p less than 0.001), patients with high Hb F levels having macrocytosis confirmed by microhematocrit studies. Patients with alpha-thalassemia had a lower MCHC than patients with four alpha-globin genes and this was not significantly affected by the level of Hb F. The combination of alpha-thalassemia and high levels of Hb F appears to result in a distinctive S/S phenotype that is similar to the type of S/S disease described in Southern India.