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Query: UMLS:C0039730 (thalassemia)
 10,305 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A rapid and inexpensive polymerase chain reaction (PCR) based strategy is described which detects the three common, severe alpha thalassaemia determinants observed in southeast Asia (--SEA) and the Mediterranean (--MED and -(alpha)20.5). Oligonucleotide primers have been chosen which allow specific identification of both normal (alpha alpha) and abnormal (--) chromosomes using identical conditions in either the same or parallel PCR reactions. This strategy should be useful in the development of screening programmes to identify carriers of alpha thalassaemia (--/alpha alpha) and prenatal diagnosis of the Hb Bart's hydrops fetalis syndrome (--/--) for those populations in which this represents a major cause of perinatal death.
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PMID:A PCR-based strategy to detect the common severe determinants of alpha thalassaemia. 152 Jun 7

zeta-Globin chain expression in carriers of a number of deletional alpha-thalassemias is investigated by radioimmunoassay. In a few cases, zeta-globin mRNAs are also studied. zeta-Globin chains are detected in (--SEA/), (--MED/), and (--SPAN/) deletions, but not in six other deletional mutations. These results suggest that the DNA element capable of suppressing zeta-globin expression in adult erythroid cells is present within the (--SPAN/) deletion, while the DNA fragment between the 5' breakpoints of the (--SA/) and the (--SEA/) deletions may contain sequences necessary for augmenting zeta-globin expression in adult erythroid cells. Furthermore, zeta-globin chains are shown by an immunocytologic technique to be present in all circulating erythrocytes in carriers of the (--SEA/) and (--MED/) deletions. This simple immunocytologic test is highly sensitive and specific to detect adult carriers of either the (--SEA/) or (--MED/) deletions, and can be used for the detection of couples at risk of pregnancies involving fetuses with homozygous alpha-thalassemia.
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PMID:Human embryonic zeta-globin chain expression in deletional alpha-thalassemias. 162 4

The results of a programme for the study of atypical familial microcytosis are analysed in this paper. The techniques used were "in vitro" synthesis of globin chains in tritiated leucine-labelled reticulocytes and genetic mapping with different restriction enzymes, plus the usual hematologic values. Of the 134 syntheses performed, 73 showed alpha/beta ratio lower than 1 (alpha-thalassaemia). The lowest values, alpha/beta ratio of 0.54 +/- 0.14, corresponded to 3 patients with Hb H disease. In general terms, our findings are similar to those reported in the literature. The genetic mapping was performed in 98 patients with alpha-thalassaemia (73 cases with decreased alpha/beta ratio, 2 cases with normal ratio, and 23 relatives). Of the 98 patients, 3 had Hb H disease, 70 corresponded to heterozygous alpha 0-thalassaemia, 11 to homozygous alpha(+)-thalassaemia, and 14 to heterozygous alpha (+)-thalassaemia. The analysis of DNA revealed the heterogeneity of the molecular alterations, the prevalent haplotypes being (--MED), in 74% of the patients, and (-3.7 alpha), in 100% of the cases. The other alpha zero-thalassaemia mutations found were the deletions (--SEA) and (--SPAN) and the "no-deletion" thalassaemias.
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PMID:[Analysis of a program for atypical familial microcytosis. Molecular basis of alpha-thalassemia]. 227 39

The results of a programme for the study of atypical familial microcytosis are analysed in this paper. The techniques used were "in vitro" synthesis of globin chains in tritiated leucine-labelled reticulocytes and genetic mapping with different restriction enzymes, plus the usual haematimetric values. Of the 134 syntheses performed, 73 showed alpha/beta ratio lower than 1 (alpha-thalassaemia). The lowest values, alpha/beta ratio of 0.54 +/- 0.14, corresponded to 3 patients with Hb H disease. In general terms, our findings are similar to those reported in the literature. The genetic mapping was performed in 98 patients with alpha-thalassaemia (73 cases with decreased alpha/beta ratio, 2 cases with normal ratio, and 23 relatives). Of the 98 patients, 3 had Hb H disease, 70 corresponded to heterozygous alpha zero-thalassaemia, 11 to homozygous alpha(+)-thalassaemia, and 14 to heterozygous alpha(+)-thalassaemia. The analysis of DNA revealed the heterogeneity of the molecular alterations, the prevalent haplotypes being (- -MED), in 74% of the patients, and (-3.7 alpha), in 100% of the cases. The other alpha zero-thalassaemia mutations found were the deletions (- -SEA) and (- -SPAN) and the "no-deletion" thalassaemias.
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PMID:[Analysis of a program for atypical familial microcytosis. Molecular basis for alpha-thalassemia. GEHBTA]. 236 92

Analysis of alpha-thalassemia syndromes in several German families revealed DNA deletion as well as non-deletion forms as the molecular basis for the defects. Thus, the alpha-thalassemia haplotype was identified as the (-alpha)3.7 rightward deletion form, and the region of the putative recombination process generating such a deletion was further characterized. In addition three different alpha(0)-thalassemia haplotypes, (--)MED, (--) > 26, and (alpha alpha)T, could be detected using alpha- and zeta-globin gene-specific probes.
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PMID:Heterogeneity of the alpha-globin gene defects in German alpha-thalassemia affected families. 299 33

We have determined the alpha-thalassaemia (alpha-thal) determinants in 78 patients with Hb H disease from Cyprus; 25 were Turkish Cypriots and 53 were Greek Cypriots. Four deletional and three non-deletional alpha-thal alleles were present; the -alpha(3.7 kb) alpha-thal-2 and the --MED-I alpha-thal-1 were most frequently seen; --MED-II and -(alpha)20.5 deletions occurred at considerably lower frequencies. About 15% of all chromosomes carried a non-deletional alpha-thal-2 allele; of these the 5 nucleotide (nt) deletion at the first intervening sequence (IVS-I) donor splice site was present in approximately 8% of all chromosomes. Two types of polyadenylation signal (poly A) mutations were observed. No striking frequency differences were seen between Greek and Turkish Cypriot patients. Combinations of the various types of alpha-thal resulted in eight different forms of Hb H disease. The phenotypes were comparable except for great variations in the level of Hb H which was highest (average approximately 22%) in the 12 patients with the alpha 5nt alpha/--MED-I combination. One patient with the same form of Hb H disease but with an additional beta-thal (IVS-I-110,G-->A) heterozygosity had a most severe microcytosis and hypochromia with < 1% Hb H. Variations in the level of Hb H might correlate with the severity of the disease, although this was not evident from the haematological data.
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PMID:alpha-Thalassaemia in the population of Cyprus. 773 46

We have estimated the incidence and molecular basis of alpha-thalassemia in a Portuguese population, mostly from the Greater Lisbon area. In a group of 100 consecutive cord blood samples, the gene frequency of the rightward deletion (-alpha 3.7) was 0.035, and the leftward deletion (-alpha 4.2) was 0.015. In this group, we have also found four heterozygotes for the triple alpha-globin gene rearrangement (alpha alpha alpha anti 3.7. gene frequency 0.020). We have characterized the subtypes of -alpha 3.7 and alpha alpha alpha anti 3.7 rearrangements. On the whole, these results give an incidence of 10% for deletional alpha-thalassemia carriers in the studied Portuguese population. In a group of 342 subjects presenting beta-thalassemia, or Hb S trait, beta-thalassemia major sickle cell disease or low red blood cell indices, the -alpha 3.7, -alpha 4.2, -SEA, -MED, (alpha alpha)MM, and alpha alpha alpha anti 3.7 haplotypes were found in different combinations. Only one nondeletional alpha-thalassemia determinant (a 5 nucleotide deletion in the alpha 2-globin gene in the second intervening sequence donor site) was detected, which might suggest a low incidence of these defects in the Portuguese population.
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PMID:Molecular basis of alpha-thalassemia in Portugal. 871 93

A total of 25 unrelated Hb H patients were studied at the DNA level. Ten different genotypes were found to be responsible for the disease. The most prevalent alpha-thalassemia-2 determinant was the alpha alpha/-alpha (3.7) kb deletion (56%) which was followed by a nondeletional type of alpha-thalassemia, namely the pentanucleotide deletion in the 5' first intervening sequence splice junction [alpha(-5nt) alpha] (16%). The two most frequent alpha-thalassemia-1 determinants were alpha alpha/-20.5 kb and alpha alpha/-17.5 kb (MED-I) deletions. In two patients, homozygosity for the polyadenylation signal mutation [alpha (PA-2)alpha] was found to be responsible for Hb H disease. Clinical and hematological expression seems more severe in patients with the alpha (-5nt) alpha deletion at the donor site of the first intervening sequence and the alpha(PA-2) alpha mutation in trans to an alpha-thalassemia-1 determinant. Homozygosity for the alpha (PA-2)alpha mutation was also found to be associated with severe phenotype.
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PMID:The molecular basis of Hb H disease in Turkey. 902 22

A neonatal screening survey of alpha-thalassemia (alpha-thal) among the United Arab Emirates (UAE) nationals was conducted on 418 consecutive cord blood samples. Our findings demonstrate that 49% of the cases studied were found with an alpha-globin gene defect. The gene frequency of the -alpha3.7 was 0.2847 and that of the -alpha4.2 was 0.0072. Four nondeletional alpha-thal mutations were found; alphaPA-1, alphaPA-2, Hb CS and alpha-5nt del with gene frequencies of 0.0036, 0.0012, 0.0024, and 0.0072, respectively. We also report here the genotype-phenotype correlation in 22 patients with Hb H disease or Hb H-like syndrome. Of these, 6 were homozygous for the alphaPA-1 mutation, 2 were homozygous for Hb CS, and 14 were compound heterozygous for either alphaPA-1, Hb CS, alpha-5nt del or --MED-I, with the -alpha3.7. The data reported here demonstrate that a considerable heterogeneity of alpha-thal mutations occurs in the UAE and that the incidence of alpha-thal in the indigenous population is one of the highest in the world. Our clinical data suggest that Hb H disease in the UAE has, in general, a mild to moderate phenotypic presentation.
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PMID:alpha-thalassemia in the United Arab Emirates. 969 Nov 47

In this report we describe a case of Hb H disease due to the interaction of the --(MED 1) deletion with a new alpha(+)-thalassemia determinant. The molecular analysis of the proband's genomic DNA was carried out by polymerase chain reaction amplification and sequencing of both alpha genes of the alpha(+)-thalassemia chromosome and revealed a deletion of codon 62 of the alpha1 gene. This DNA triplet codes for a valine residue at the E11 alpha helix, which is located in the interior of the heme pocket. Substitutions of valine E11 with other amino acid residues in the alpha as well as beta polypeptide chains lead, in the heterozygous carrier, either to Hb M disease or to congenital non-spherocytic hemolytic anemia. We assume that the deletion of valine at alpha62(E11) disrupts the conformation of the alpha chain to such an extent that the mutated subunit is rapidly removed by proteolysis. The final result is an alpha-thalassemia phenotype rather than an unstable hemoglobin syndrome. This conclusion is supported by the apparent absence of an abnormal alpha chain in the peripheral blood of the patient.
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PMID:Hb Aghia Sophia [alpha62(E11)Val-->0 (alpha1)], an "in-frame" deletion causing alpha-thalassemia. 1056 20


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