Alpha-beta thalassemia disease in a Negro family

Hematological phenotype of the double heterozygous state for alpha and beta thalassemia

In this study, we have correlated the hematological phenotype of 56 Sardinian beta o-thalassemia heterozygotes with their alpha-globin genotype as defined by restriction endonuclease mapping. We found that the coinheritance of the deletion of one alpha-globin and, more obviously, two alpha-globin genes tend to normalize the thalassemia-like hematological phenotype commonly associated with the beta o-thalassemia carrier state. On the other hand, the association of the deletion of three alpha-globin genes caused a more severe phenotype. By globin chain synthesis analysis, those beta o-thalassemia heterozygotes with the (-alpha/alpha alpha) alpha-globin genotype had less deficiency of beta-chain synthesis than did those with the normal alpha-globin genotype (alpha alpha/alpha alpha). In heterozygotes with the (-alpha/-alpha) and in those with the (--/-alpha) alpha-globin genotype the imbalance was actually reversed with a mild or marked alpha-chain synthesis excess respectively.

Molecular mechanism accounting for milder types of thalassemia major

We carried out alpha-globin gene analysis by restriction endonuclease mapping in 91 Sardinians with homozygous transfusion-dependent beta 0-thalassemia and correlated the clinical findings with the alpha-globin genotype. In patients (n = 6) with deletion of two alpha-globin structural genes, disease onset and transfusion dependence occur later than in those (n = 50) with a full complement of alpha-globin genes. There was no statistically significant difference in the group of patients (n = 35) with deletion of only one alpha-globin gene. Patients with deletion of two alpha-globin genes had significantly higher Hb A2 levels than those with a full complement of alpha-structural genes and those with deletion of a single alpha-globin gene. From this and other studies, it seems that the deletion of two alpha-globin structural genes may convert the common severe clinical picture associated with homozygous beta 0-thalassemia to milder forms, ranging from a later occurring but still transfusion-dependent type to a non-transfusion-dependent form.

Influence of two alpha-globin gene deletions on homozygous beta 0-thalassemia

The favorable influence of alpha-thalassemia due to a deletion of two alpha-globin genes (alpha-thal-l) on homozygous beta 0-thalassemia in an adult Chinese woman is described. Her clinical and hematologic condition was milder than usually seen in homozygous beta 0-thalassemia. With the help of repeated blood transfusions immediately before delivery she gave birth to a physically healthy baby who had the alpha-thal-l trait due to two alpha-globin gene deletions with Hb Bart's in the cord blood.

Interaction of alpha and beta thalassaemia genes in two Sardinian families

Our paper describes two Sardinian families with alpha-beta thalassaemia interaction. In the first (family S), the propositus, whose haemoglobin pattern at birth consisted of about 25% Hb Bart's and 75% Hb F, successively developed a clinical and haematological picture typical of Cooleys anaemia. Haematological and globin chain synthesis studies together with these findings suggest that he is homozygous for beta 0 thalassaemia and heterozygous for alpha thalassaemia-1 and alpha thalassaemia-2. This conclusion is further substantiated by the finding of various combination of alpha and beta thalassaemia among his family members. In the P family two twins whose haemoglobin pattern and synthesis data at birth were similar to those of the proband of family S died in the neonatal period. The mother was assumed to be a compound heterozygte for alpha thalassaemia-2 and beta 0 thalassaemia and the father for alpha thalassaemia-1 and beta 0 thalassaemia. The homozygous state for beta 0 thalassaemia in association with the alpha thalassaemia 1 and alpha thalassaemia 2 genes results in a severe clinical picture similar to that of a homozygous beta 0 thalassaemia. The interaction between the heterozygous state for beta 0 thalassaemia and the alpha thalassaemia 1 or alpha thalassaemia 2 genes, or the combination of both, results in a haematological picture similar to that of a beta thalassaemia heterozygote.

Thalassaemia of intermediate severity resulting from the interaction between alpha- and beta-thalassaemia

A Sicilian family is described in which the alpha-thalassaemia gene is interacting in several members with beta-thalassaemia resulting in a balanced alpha/beta chain production ratio. In one patient, affected by homozygous beta-thalassaemia, the presence of alpha-thalassaemia resulted in a less severe clinical expression of the disease, less marked imbalance in the alpha/non-alpha ratio, and a lower level of HbF. Further studies of haemoglobin synthesis are needed to clarify the complex genetic picture that results from the interaction of different forms of thalassaemia.

A unique thalassaemic syndrome: homozygous alpha-thalassaemia + homozygous beta-thalassaemia

The disturbed balance of globin chain synthesis is a major factor in the pathophysiology of the thalassaemic disorders; this concept is strongly supported by the study of a patient displaying an extreme but symmetrical deficit of both major types of chains alpha and beta. The patient had a mild clinical picture but presented a striking hypochromia (MCH 10 pg) with compensatory erythrocytosis (RBC 10(12)/l.). Study of the propositus and his family by haematological, biochemical and biosynthetic techniques indicates that the patient carries two alpha- and two beta-thalassaemia genes resulting in balanced globin chain synthesis; in addition, several members of the family carry two or three abnormal genes. During observation a change in the haematological pattern occurred with a shift towards more intensive beta-chain and away from gamma-chaim synthesis; this appeared with be associated with improvement of his anaemia through more effective erythropoiesis.

alpha-Thalassemia and beta-thalassemia in a Turkish family

A Turkish family is described in which three children have a clinical picture similar to that of thalassemia major, with typical red cell morphology and indices, and with about 10% Hb Bart's but without measurable amounts of Hb H. Hematological evaluation of six members of this family that included in vitro hemoglobin synthesis suggests that beta-(or delta beta-) thalassemia, beta-silent thalassemia, and mild and severe alpha-thalassemia genes are present in different combinations. The data indicate that beta/alpha chain ratios in patients with more than one type of thalassemia should be evaluated in relationship to values obtained for several relatives even though some of the thalassemia determinants may be silent in the parents.

Mild thalassemia: the result of interactions of alpha and beta thalassemia genes

Homozygous thalassemia is due to inherited unbalanced synthesis of the alpha- or beta-chains of hemoglobin. Clinical severity may be in part related to the extent of alpha:beta imbalance. Two families are presented that illustrate this concept. Thalassemia in these individuals was evaluated by clinical and genetic criteria. The relative rates of alpha- and beta-chain synthesis in their reticulocytes were estimated by the extent of incorporation of 1-leucine-U-(14)C into the chains. Unusual combinations of clinical and hematological data and biosynthetic ratios were obtained in certain individuals which indicated the presence of combinations of alpha- and beta-thalassemia genes. The propositus of the first family had mild Cooley's anemia and was believed to have one alpha- as well as two beta-thalassemia genes. Presumably the alpha-thalassemia gene interfered with alpha-chain production which lead to less accumulation of alpha-chains and a reduced rate of intramedullary and peripheral hemolysis. In the second family two individuals were believed to have an alpha-thalassemia, a "silent carrier," and a beta-thalassemia gene. Despite the fact that they appeared to have the genotype of hemoglobin H disease, their cells contained no hemoglobin H and had a normal lifespan presumably because excess beta-chain production was inhibited by the beta-thalessemia gene. These family studies suggest that the alpha:beta imbalance observed in thalassemia may be favorably influenced by combinations of alpha- and beta-thalassemia genes.