Medicina: Ematologia: Talassemie e trapianto del midollo osseo
| English |
| alpha-thalassemias |
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| Attestation |
3
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| Part of speech |
Noun syntagm
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| Grammatical label |
Countable
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| Variant |
a-thalassemia, a thalassemia, alfa thalassemia, a-thal
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| Definition |
The clinical expression of a-thalassemia is very complex, not only because the underlying molecular defects are heterogeneous but also because the involved genes are four, having different degrees of expression and compensation. In analogy to b-thalassemia, decreased a-chain synthesis may result from deletions or mutations of the a genes and the flanking regulatory elements. The deletions involve one (-a) or both (--) genes on each chromosome. The (-a) thalassemias result from nonhomologous unequal recombinations which are facilitated by the great homology of the DNA sequences which lie across the a gene cluster including the two a genes (boxes x, y, z). The crossovers occur either between the x box upstream of the a2 gene on one chromosome and the homologous box upstream of the a1 gene on the other or between the z box which includes the a2 gene on the one chromosome and its homologous box including the a1 gene on the other.
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| Definition source |
Loukopoulos, D. (1991). ‘Thalassemia: genotypes and phenotypes’. Annals of Hematology 62(4):85-94. Review. (RISCEN96)
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| Context |
a-Thalassemia is another well-established unlinked ameliorating factor in b-thalassemia homozygotes. The absence of two a-genes resulting in lesser severity of the clinical course is well documented.
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| Context source |
Nadkarni, A., et al. (2001). ‘Molecular pathogenesis and clinical variability of beta-thalassemia syndromes among Indians’. American Journal of Hematology 68(2):75-80. (RISCEN161)
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| Subject field |
Haemopoiesis
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| Generic concept |
Thalassemias, microcythemia
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| Specific concept |
alpha-talassemia 1, alpha-talassemia 2, alpha-talassemia 3, hydrops fetalis, HbH disease
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| Coordinate concept |
Beta-thalassemias
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| it |
Alfa-talassemie
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| Reliability code |
3
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