Molecular analysis of alpha- and beta-thalassemia in Meizhou region and comparison of gene mutation spectrum with different regions of southern China.

BACKGROUND: Thalassemia is a group of inherited autosomal recessive hemolytic anemia disease caused by reduced or absent synthesis of globin chain/chains of hemoglobin. Only few studies showed the molecular characterization of α- and ß-thalassemia in Meizhou city of China. METHODS: A total of 22,401 individuals were collected; hematological and hemoglobin electrophoresis analysis and thalassemia genetic testing were performed. RESULTS: Eleven thousand and thirty (49.24%) cases with microcytosis (mean corpuscular volume (MCV) < 82 fl), 11,074 (49.44%) cases with hypochromia (mean corpuscular Hb (MCH) < 27 pg) in 22,401 subjects, 11,085 cases with abnormal hemoglobin results were identified in subjects aged ≥6 months. 7,322 (32.69%) subjects harbored thalassemia mutations, including 4,841 (21.61%) subjects with α-thalassemia, 2,237 (9.99%) with ß-thalassemia, and 244 (1.09%) with α-thalassemia combined ß-thalassemia. 18 genotypes of α-thalassemia mutations and 27 genotypes of ß-thalassemia mutations were characterized. The most frequent α gene mutation was --SEA (64.69%), followed by -α3.7 (19.93%), -α4.2 (7.73%), αCS α (3.97%), and αWS α (2.83%). The six most common ß-thalassemia mutations were IVS-II-654 (C>T) (39.79%), CD41-42 (-TCTT) (33.02%), -28 (A>G) (10.38%), CD17 (A>T) (9.08%), CD27-28 (+C) (2.14%), and CD26 (G>A) (2.02%). In addition, MCV and MCH were sensitive markers for α- and ß-thalassemia except for -α3.7 /αα, -α4.2 /αα, αCS α/αα, αWS α/αα, and ßCap+40-43 /ßN . CONCLUSIONS: The --SEA , -α3.7 , and -α4.2 deletions were the main mutations of α-thalassemia, while IVS-II-654 (C>T), CD41-42 (-TCTT), -28 (A>G), and CD17 (A>T) mutations of ß-thalassemia in Meizhou. There were some differences in thalassemia mutation frequencies in Meizhou city from other populations in China.

Implications of Population Screening for Thalassemias and Hemoglobinopathies in Rural Areas of West Bengal, India: Report of a 10-Year Study of 287,258 Cases.

Thalassemia and hemoglobinopathies are the most common cause of high morbidity and mortality in India. Detection of carriers and premarital counseling play an important role in preventing the birth of a thalassemic child. The present study aimed to detect large numbers of asymptomatic carriers in rural areas of West Bengal, India. The present cross-sectional study was conducted over a period of 10 years. Thalassemia awareness programs and detection camps were organized at the community level. After signed written consent was obtained, the collected blood samples were subjected to a complete blood count (CBC) in an automated blood cell counter and then analyzed by high performance liquid chromatography (HPLC); in difficult cases, samples were sent to the reference laboratory for molecular characterization. Out of 287,258 samples collected, 32,921 (11.46%) cases revealed abnormal hemoglobins (Hbs); of these, 31,782 (11.06%) carried heterozygous states (carriers/traits), and the remainder were either homozygous or compound heterozygous for different hemoglobinopathies. Two common variants were revealed in the study, namely ß-thalassemia (ß-thal) (7.23%) and Hb E [ß26(B8)Glu→Lys, HBB: c.79G>A] (2.77%) traits. Among homozygous or compound heterozygous states, Hb E/ß-thal (0.14%) and ß-thal major (ß-TM) (0.12%) were predominant. In rural areas of West Bengal, the most common Hb variants detected were ß-thal and Hb E traits. In view of the high prevalence of hemoglobinopathies in this region, routine premarital screening and genetic counseling should be emphasized and encouraged to prevent the birth of a thalassemic child, and thus curtailing the burden on families and the health economy.

ATRX and the replication of structured DNA.

Understanding the underlying molecular basis for disease can often be a prolonged and tortuous process with many false leads and blind alleys. Relating the cause of ATR-X syndrome to the function of the protein ATRX is a case in point. In this review we attempt to bring together the diverse biological phenomena associated with ATRX dysfunction with what has recently been discovered concerning the chromatin remodelling activity of this protein. This potentially casts light on how defective DNA replication/histone replacement can impact on transcription, telomere maintenance and also possibly chromosome segregation.

Erythrocyte density in sickle cell syndromes is associated with specific clinical manifestations and hemolysis.

Dense, dehydrated red blood cells (DRBCs) are a characteristic feature of sickle-cell disease (SCD). DRBCs play a role in the pathophysiology of SCD acute and chronic organ damage because of heightened tendency to undergo polymerization and sickling because of their higher hemoglobin S concentration. Relations between red cell density (assessed with phthalate density-distribution profile method) and several hematologic, biochemical, genetic parameters, and clinical manifestations were studied in a large cohort of homozygous patients. The percentage of DRBCs was significantly higher in patients who experienced skin ulcers, priapism, or renal dysfunction. Presence of α-thalassemia deletions was associated with fewer DRBCs. A multivariable analysis model showed DRBCs to be positively associated with hemolytic parameters such as lactate dehydrogenase and bilirubin and negatively with fetal hemoglobin. The percentage of DRBCs decreased by 34% at 6 months of hydroxycarbamide (xydroxyurea) therapy. Thus, DRBCs are associated with specific clinical manifestations and biologic markers and may be a useful addition to the biologic and clinical evaluation of patients with SCD, because they can easily be measured in a hematocrit tube.

[Spectrum of gene deletion in 471 children with α-thalassemia].

OBJECTIVE: To study the distribution of common α-thalassemia gene deletion in children. METHODS: Blood cell analysis was performed on children who visited the clinic of the Foshan Women and Children's Hospital. Blood samples (2 mL, EDTA anticoagulant) was collected from children with MCV<82 fl for analysis of α-thalassemia gene using the GAP-PCR method. RESULTS: MCV<82 fl was found in 1341 children. Of the 1341 children, 471 (35.1%) were diagnosed with α-thalassemia. The prevalence of α-thalassemia increased with increasing age. --SEA was a major type of α-thalassemia gene deletion (75.3%), followed by -a3.7 (17.0%) and -a4.2 (7.7%) in the 471 patients. The top three genotypes were --SEA/aa (73.2%), aa/-a3.7 (12.5%) and --SEA/-a3.7 (5.5%). CONCLUSIONS: Genetic testing is necessary for the diagnosis of α-thalassemia in children with MCV<82 fl. --SEA is a common type of α-thalassemia gene deletion, and -SEA/aa is a common gene type of α-thalassemia in the subjects of this study.

[The first case of acquired hemoglobinopathy H in Russia in a patient developing unclassified myelodysplastic syndrome/myeloproliferative disease].

A 55 year-old man with hemolytic anemia is described. Careful clinical and laboratory studies showed that this condition was a manifestation of non-hereditary hemoglobinopathy N. The clinical symptoms suggested acquired hemoglobinopathy N that devloped parallel to myelodysplastic syndrome/myeloproliferative disease.

Two cases of non-haematological cause of fetal hydrops in at-risk pregnancies for homozygous α0-thalassemia.

In recent years, sonography has been successfully used as an alternative method for prenatal detection of Hb Bart's disease in areas with high prevalence of α-thalassemia. We present two cases in which the fetuses demonstrated signs of Hb Bart's disease by sonography, however, invasive procedures could not confirm it. We recommend that, in prenatal diagnosis of Hb Bart's disease by sonography, the diagnosis should always be confirmed with definitive methods to exclude false-positive findings.

Secondary erythrocytosis caused by hemoglobin Tak/(뫧)0-thalassemia syndrome.

Secondary erythrocytosis may arise from several causes, but an association with oxygen transport is rare. We describe for the first time a form of secondary erythrocytosis caused by compound heterozygosity for hemoglobin (Hb) Tak and (δß)(0)-thalassemia found in an adult Thai individual. The patient had marked erythrocytosis and microcytosis with increased Hb and hematocrit values. Hb analyses using the Hb Gold Analyzer showed Hb A2 (72.5%) and Hb F (30.0%) without Hb A while the capillary electrophoresis revealed 2.3% Hb A2 and a major peak of Hb F (91.2%). Further molecular investigation identified that he was in fact a compound heterozygote for Hb Tak and deletional (δß)(0)-thalassemia. Hematological parameters of the patient were compared with those observed for a Thai boy who demonstrated features of erythrocytosis and microcytosis caused by homozygous Hb Tak with α(+)-thalassemia and with those of pure carriers of Hb Tak and (δß)(0)-thalassemia in our series. This report confirms the importance of both Hb and molecular investigations for the assessment of genotype/phenotype correlation and the appropriate management of the patients.

Acquired haemoglobin H disease associated with myelodysplastic syndrome.

A 60-year-old male patient presented with jaundice. Initial investigations showed anemia, indirect hyperbilirubinemia, raised Lactic Dehydrogenase (LDH) and increased reticulocyte count suggestive of hemolysis. Considering hemolysis low MCV and basophilic stippling on peripheral film, hemoglobin electrophoresis was done that showed Haemoglobin H (15.5%) that in the absence of family history was thought to be acquired. After bone marrow examination, the final diagnosis was Myelodysplastic Syndrome (MDS), Refractory anemia with excess of blast (RAEB) associated with acquired Haemoglobin H (Hb H) disease.

Consanguinity affects selection of alpha-thalassemia genotypes and the size of populations under selection pressure from malaria.

BACKGROUND: In populations with alpha(+)-thalassemia gene deletion, the practice of consanguineous marriages is common. AIM: The study explored the impact of consanguinity (inbreeding) on the selection of alpha(+)-thalassemia genotypes in a computer model. METHOD: In a population under selection pressure from malaria, a single protective mutation (-alpha/alphaalpha genotype) was introduced among normal genotypes (alphaalpha/alphaalpha), and mating allowed to proceed. Heterozygote (-alpha/alphaalpha) and homozygote (-alpha/-alpha) children were 1.5 and 2.5 times more likely to survive malaria than those with normal genotypes. Using different coefficients of inbreeding (F, range 0-0.12), we examined the effect of population size, and the mean number of generations required for the homozygote frequency to reach 0.5. RESULTS: On average, consanguineous populations were larger than randomly mating populations and the size was directly proportional to F. In more inbred populations,-alpha/-alpha homozygotes reached a frequency of 0.5 faster than in less inbred populations. As the frequency of the alpha(+)-thalassemia allele in a population increases, however, the positive effect of inbreeding on the population growth decreases. CONCLUSION: Under selection pressure from malaria, consanguinity may increase the speed of selection of-alpha/-alpha homozygotes and provide an advantage regarding population growth over non-consanguineous populations.

Prevalence of erythrocyte haemoglobin H inclusions in unselected patients with clonal myeloid disorders.

Patients with clonal myeloid disorders, especially myelodysplastic syndromes (MDS), may acquire alpha-thalassaemia. To estimate the prevalence of this erythrocyte phenotype, we examined brilliant cresyl blue-stained blood smears from 201 patients with neoplastic myeloid disorders and 282 controls (195 non-clonal anaemia, 62 with medical illnesses without anaemia and 25 healthy persons). Haemoglobin H inclusions were detected in 8/100 patients with MDS (8%) and 2/81 (2.5%) patients with myeloproliferative disorders, but in none of the acute leukaemia patients or controls. We conclude that the emergence of thalassaemic clones may be relatively common in the disordered marrow milieu of MDS.

[Acquired alpha-thalassemia as early sign for myelodysplastic syndrome (refractory anaemia) with secondary haemochromatosis]. / Alpha-thalassémie acquise révélatrice d'un syndrome myélodysplasique de type anémie réfractaire avec hémochromatose secondaire.

We report the case of a 59 year old man presenting a regenerative microcytic hypochromic anaemia. The investigations revealed the presence of haemoglobin H, suggesting abnormalities in the alpha-globin chains synthesis. Alpha-thalassemia was thus suspected. The patient had no personal or familial history. The association with aniso-poïkilocytosis and a marked iron overload (ferritinemia > 1,500 microg/L) suggested a myelodysplastic syndrome, which was confirmed with a bone marrow aspiration. The pattern was consistent with the Acquired alpha-Thalassemia-Myelodysplastic Syndrome (ATMDS). About a hundred cases are listed worldwidely and collected in an international registry. The causes of ATMDS are ignored, but recent reports indicate that the ATRX gene may be implicated in the pathogenesis. ATRX is a chromatin-associated protein, involved in the transcription of several genes. The alpha globin genes could be one of the targets of the ATRX protein.

Carrier screening for alpha- and beta-thalassemia in pregnancy: the results of an 11-year prospective program in Guangzhou Maternal and Neonatal hospital.

OBJECTIVES: To evaluate the first prospective screening program in China for control of alpha and beta-thalassemia in the population of pregnant couples. METHODS: During the period between January 1993 and December 2003, a hospital-based preventive program was conducted at the biggest birth center in Guangzhou, with 1/17 of all deliveries in this city referred annually by use of conventional heterozygote screening strategy in combination with the system of regular healthcare examination in pregnancy. RESULTS: The screened records included 49 221 pregnant women, and 4503 husbands of the pregnant women showed positive on the screening test. Of the at-risk couples, there were 198 for alpha-thal (4.4%) and 83 for beta-thal (1.8%), respectively. Genetic counseling was offered to all at-risk couples and a successful prenatal diagnosis was performed for 269 out of 281 (95.7%) for alpha- or beta-thal major, with the remaining 12 couples refusing to accept prenatal diagnosis. Out of 187 pregnancies at risk for homozygous alpha0-thal and 82 at risk for beta-thal major, 51 hydrops fetalis with Hb Bart's and 18 beta-thal major were identified. All pregnancies with affected fetuses were voluntarily terminated, leading to a marked reduction of severe alpha- and beta-thal births at this hospital since the program has been launched. CONCLUSIONS: Our hospital-based program proved to be highly effective in reducing severe thals in pregnant populations.

Dinucleotide deletion in -alpha3.7 allele causes a severe form of alpha+ thalassaemia.

We describe a family of Italian origin in which the father and his two children had hypochromia and microcytosis with normal iron status. All individuals underwent an uneventful clinical course and required no treatment. To investigate the molecular basis of this phenotype, which is a prerequisite for further genetic counselling, we revealed that all affected family members are carriers of a common form of alpha+ thalassaemia resulting from the deletion of 3.7 kb of the alpha-globin cluster (alphaalpha/-alpha3.7). However, this genotype alone could not account for the phenotype presenting in this family. Further characterization of the alpha-globin genes demonstrated an additional AC deletion in the vicinity of the initiation codon of the -alpha3.7 allele. This secondary mutation causes an additional impaired translation of the affected allele producing increased globin chain imbalance. This leads to a more severe phenotype, as heterozygotes for such mutation (alphaalpha/-alphaT) have hypochromic microcytosis and abnormal globin chain synthesis that mimic alpha0 thalassaemia trait (--/alphaalpha). Accurate genotyping of alpha globin determinant is absolutely required as there is a possibility that an interaction of this unusual double mutation with other common alpha0 thalassaemias (--/-alphaT) can give rise to a very severe, probably fatal, alpha thalassaemia.

Hemoglobin H disease resulting from the association of the - alpha 3.7 rightward deletion and the (alpha alpha)MM deletion in a Brazilian patient.

A patient with Hb H disease resulting from the association of the - alpha 3.7 rightward deletion with the rare (alpha alpha)MM deletion, which removes the entire alpha-major regulatory element (MRE), is reported. This is the first description of an alpha-thalassemic mutation resulting from deletion of the locus-controlling sequences in the South-American population.

Pathophysiology of alpha- and beta-thalassemia: therapeutic implications.

At the molecular level, the underlying cause of thalassemia is any of a number of genetic lesions that reduce or abolish the production of the globin chains of hemoglobin. The resulting chain imbalance is the key factor initiating the damage to the red blood cell (RBC) and it is the major pathophysiological event in all forms of the thalassemia syndromes. In this review we will outline some of the cellular and systemic processes that have been implicated in the development of the disease. When relevant, we will discuss the ways in which these processes can be altered in a therapeutic manner.