Cases reported "Hemoglobinopathies"

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1/3. Interaction of two different disorders in the beta-globin gene cluster associated with an increased hemoglobin F production: a novel deletion type of (G) gamma ((A) gamma delta beta)(0)-thalassemia and a delta(0)-hereditary persistence of fetal hemoglobin determinant.

    We report two different disorders of the beta-globin gene cluster segregating in a Belgian family: a novel deletion that results in (G) gamma ((A) gamma delta beta)(0)-thalassemia (thal) and a heterocellular hereditary persistence of foetal hemoglobin of the Swiss type linked to a delta(0)-thal gene (delta (0)-HPFH). Heterozygosity for the heterocellular HPFH brings about a moderate (3.4% to 8.24%) increase of hemoglobin (Hb) F having a G gamma/A gamma ratio of 4:1, whereas carriers of the G gamma ((A) gamma delta beta)(0)-thal deletion show in their peripheral blood a considerably higher (15%) percentage of Hb F. Both defects interact in the compound heterozygotes for G gamma ((A) gamma delta beta)(0)-thal and delta(0)-HPFH producing a further increase (up to 24%) of fetal Hb consisting entirely of G gamma chains. Molecular characterization of the (G) gamma ((A) gamma delta beta)(0)-thal by means of Southern analysis showed that the deletion spans about 50 kb, removing the 3' end of the A gamma-gene, the psi beta-, delta-, and beta-genes. A number of possible mechanisms leading to the overproduction of Hb F in HPFH and (G) gamma ((A) gamma delta beta)(0)-thal will be discussed.
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2/3. A non-deletion hereditary persistence of fetal hemoglobin (HPFH) determinant not linked to the beta-globin gene complex.

    We describe an Asian Indian family with a non-deletion form of hereditary persistence of fetal hemoglobin (HPFH) and beta zero thalassemia. The propositus who has homozygous beta zero thalassemia has an unusually mild form of the disease which is ascribed to the co-inheritance of HPFH. The interaction of HPFH and beta thalassemia was studied in five generations of this family. Linkage analysis showed that the genetic determinant for the HPFH segregates independently from the gamma delta beta globin gene complex. Analysis of HPFH linkage to a panel of genetic markers in such a large family offers the possibility of defining a transacting locus (or loci) involved in the expression of the gamma globin gene.
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3/3. G gamma A gamma (beta ) hereditary persistence of fetal hemoglobin: the G gamma -158 C-->T mutation in cis to the -175 T-->C mutation of the A gamma-globin gene results in increased G gamma-globin synthesis.

    Hereditary persistence of fetal hemoglobin (HPFH) can be generally classified into deletional and nondeletional forms. The family described in the present study has characteristics of both types of HPFH. The proband is a healthy 30-year-old black woman. Analysis of her hemoglobin revealed 40.4% HbS, 40.9% HbF (G gamma/A gamma ratio 0.53), 16.8% HbA, and 1.9% HbA2. All of her hematologic indices were normal, and the distribution of HbF in her red cells was pancellular. family studies demonstrated that the proband has one chromosome 11 bearing the beta s-globin gene and the other bearing a G gamma A gamma (beta ) HPFH determinant in cis to the beta A-globin gene. Gene mapping studies of the region between the G gamma- and beta-globin genes were normal. However, when the A gamma and G gamma promoters were amplified by polymerase chain reaction (PCR) and sequenced, the A gamma promoter was found to have the T-->C mutation at -175, and the G gamma promoter region was found to have the C-->T mutation at -158. The -158 C-->T mutation has been associated with elevated G gamma levels and high HbF in hemolysis, although its role in causing these effects is unclear. The present study suggests that this mutation can also enhance G gamma-globin expression in cis to the -175 T-->C mutation in the absence of hemolysis. We suggest that the alteration of the A gamma gene octamer binding site by the -175 mutation, as well as the loss of a putative G gamma "silencer" caused by the -158 mutation may account for this phenotype. We propose calling these linked mutations the G gamma A gamma(beta ) HPFH.
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