A novel case of haemoglobin H disease associated with clinical and morphological characteristics of congenital dyserythropoietic anaemia type I.

We report, for the first time, an unusual case of congenital anaemia with the clinical diagnosis of haemoglobin H disease complicated by morphological features at the light and electron microscopy level very similar to those of CDA-I. The red cell indices and the globin chain biosynthetic ratio were not characteristic of the defective haemoglobin genotype. The haematological, clinical and morphological data strongly suggest the novel coexistence of the two defects in a patient. The disease is characterised by a unique dyserythropoietic phenotype of diagnostic importance, which possibly brings new data regarding the reciprocal interaction between the two diseases, especially concerning a specific abnormality in globin chain synthesis in CDA-I, as previously suggested.

Fetal hemoglobin expression in the compound heterozygous state for -117 (G-->A) Agamma HPFH and IVS-1 nt 110 (G-->A) beta+ thalassemia: a case study.

The splicing defect at IVS-I-110 is by far (43.15%) the most common beta-thalassaemia mutation in Greece. The - 117 (G-->A) Agamma hereditary persistence of fetal hemoglobin (Greek HPFH) is also the most frequent nondeletional HPFH in Greece. We report a case in which these two defects co-segregates. She is a healthy female where the total Hb is 12.3 g/dl with 51% HbF and normal HbA2. Her Ggamma/Agamma ratio is 35:65 differing from that of 10 simple heterozygotes for the Greek HPFH who have ratio of 8:92. Molecular analysis of the beta-globin genotype revealed the presence of the IVS-I-110 beta+ mutation in trans to the -117 G-->A Greek HPFH. Both mutations are linked to Ia. Her father has Greek HPFH in trans to the -158 C-->T on the Ggamma promoter, which is linked with haplotype IIIalpha. He has 13% HbF with a Ggamma/Agamma ratio 32:68. Her sister is a compound heterozygote for the IVS-I-110 mutation in trans to the - 158 C-->T, with HbF levels of 3% and a Ggamma/Agamma ratio 72:28.

Fetal hemoglobin expression in the compound heterozygous state for -117 (G-->A) Agamma HPFH and IVSII-745 (C-->G) beta+ thalassemia: a case study.

We studied a family in which two inherited defects of the non-alpha-globin cluster segregate: Greek hereditary persistence of fetal hemoglobin (HPFH) and beta-thalassemia. The compound heterozygote is a healthy man with 43% HbF, Ggamma/Agamma ratio (27:73) differing from that of 10 simple heterozygotes for the Greek HPFH (92:8), normal levels of total Hb (13.3 g/dl), and reduced HbA2 levels comparing with the levels of beta-thal heterozygotes for the same mutation. Molecular analysis of the beta-globin genotype revealed the presence of the IVSII-745 (C-->G) beta+ RNA splice mutation in trans with the -117 G-->A Greek HPFH. The beta+ mutation was linked to haplotype VII and the Greek HPFH was associated with haplotype Ia. The father of the compound heterozygote carries the Greek HPFH in trans with the -158 C-->T on the Ggamma promoter, which is linked with haplotype IV. He presented 13.5% HbF with a Ggamma/Agamma ratio 75:25. His daughter was a compound heterozygote for the IVSII-745 mutation in trans with the -158 C-->T, while her HbF levels were 3.7% with a Ggamma/Agamma ratio 31:69.

Iron mobilization from hepatocyte monolayer cultures by chelators: the importance of membrane permeability and the iron-binding constant.

A series of bidentate hydroxypyridinone iron chelators that have therapeutic potential as oral iron chelators, have been studied systematically to determine which properties are the most critical for the mobilization of hepatocyte iron. The relationship between lipid solubility of the free and complexed forms of each chelator and hepatocyte iron release has been investigated as well as the contribution of the binding constant for iron (III). Hydroxypyridin-4-ones that were approximately equally soluble in lipid and aqueous phases were the most active compounds, the partition coefficient of the free chelator appearing to be more critical in determining iron release than that of the iron-complexed form. Highly hydrophilic chelators did not mobilize intracellular iron pools, whereas highly lipophilic compounds were toxic to hepatocytes. The contribution of the binding constant for iron (III) to cellular iron release was assessed by comparing hydroxypyridin-4-ones (log beta 3 = 36) and hydroxypyridin-2-ones (log beta 3 = 32), which possess similar partition coefficients. The results show that the binding for iron (III) is particularly important at low concentrations of chelator (less than 100 mumol/L) and that at higher concentrations (greater than 500 mumol/L) iron mobilization is limited by the available chelatable pool. Measurement of iron release with other chelators confirms the importance of both the lipid solubilities and iron (III)-binding constants to iron mobilization. The most active hydroxypyridin-4-ones released more hepatocyte iron than did deferoxamine when compared at equimolar concentrations. The results suggest that the ability of an iron chelator to enter the cell is crucial for effective iron mobilization and that once within the cell the binding constant of the chelator for iron (III) becomes a dominant factor.

In vivo evaluation of hydroxypyridone iron chelators in a mouse model.

The 59Fe excretion caused by a range of bidentate N-substituted [R group = methyl (CP20), ethyl (CP21), propyl (CP22), isopropyl (CP23), butyl (CP24) or hexyl (CP25)] 3-hydroxypyrid-4-one chelators in iron-overloaded mice is presented. All the compounds cause significant iron excretion when given intraperitoneally, but that the most hydrophobic compounds, CP24 and CP25, were toxic except at low doses. The excretion caused by CP21, CP22 and CP23 were significantly greater than that caused by CP20 and slightly larger than that caused by an equivalent dose of desferrioxamine. These compounds (CP20 through CP24) also caused significant excretion of 59Fe when administered orally. Compounds CP21, CP22 and CP24 were significantly more active than compounds CP20 and CP23. It is concluded that the N-ethyl or N-propyl 3-hydroxypyrid-4-ones are the most promising compounds for clinical application. Preliminary experiments using a hexadentate pyrid-2-one, CP130, show that this causes significant 59Fe excretion both when given intraperitoneally or orally.