M. Furbetta

The interaction of α thalassaemia with heterozygous β thalassaemia

Summary. The α globin genotypes of 55 β thalassaemia heterozygotes have been determined by restriction endonuclease analysis to identify those with interacting α thalassaemia genes. A comparison of the haematological and haemoglobin synthesis findings of individuals with normal α genotypes (αα/αα) with those with one (‐ α/αα) or two (‐α/‐α) α genes deleted shows that the latter two groups have more balanced globin chain synthesis ratios, higher haemoglobin levels, and larger, better haemoglobinized red cells. This suggests that the degree of globin chain imbalance is a significant factor in determining the red cell characteristics in heterozygous β thalassaemia. Screening programmes for thalassaemia, based on the detection of low MCVs, could miss cases of the interaction of α and β thalassaemia.

PRENATAL DIAGNOSIS OF β-THALASSÆMIA AND SICKLE-CELL ANÆMIA: Experience with 24 Cases

Abstract Prenatal diagnosis of β-thalassaemia and sickle-cell anaemia was attempted in 24 pregnancies. Adequate amounts of fetal blood (for studying globin-chain synthesis) were obtained in 22 cases. 4 cases of homozygous β-thalassaemia and 2 of sickle-cell anaemia were diagnosed. The difference between the homozygous and non-homozygous states was well defined. Fetal bleeding from cord puncture and amnionitis resulted in the loss of three fetuses, and methods to avoid these complications are being devised. It is concluded that prenatal diagnosis of disorders of β-globin synthesis is feasible.

Prenatal diagnosis of homozygous β-thalassaemia.

Summary In two pregnancies at risk for homozygous (β + and β 0 thalassemia, fetal blood mixed with maternal blood was obtained by placental aspiration and was purified to over 90% purity by differential agglutination with anti-i antibodies. Study of globin-chain synthesis showed absence of β-globin chain in both fetuses. The diagnosis of homozygous β-thalassaemia was made and was confirmed after the pregnancies were terminated. Thus, the defect in β-globin-chain synthesis in homozygous β-thalassaemia is expressed in utero, and prenatal diagnosis is possible.

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.

Isoelectric Focusing of Globin Chains for Antenatal Diagnosis of β°-Thalassemia

A recently developed isoelectric focusing technique for human globin chain separation has been applied to the antenatal diagnosis of β°-thalassemia in Sardinia. Results obtained with this method show a complete concordance with those obtained by the currently-in-use chromatographic separation of globin chains by carboxymethyl-cellulose. The ease with which several samples (up to 20) can be simultaneously processed and analyzed by a single operator and the very simple equipment required make this new method ideal for the antenatal diagnosis of β°-thalassemia and could encourage a more widespread use of prenatal diagnosis of thalassemias.

Interaction of Alpha and Beta Thalassaemia Genes in Two Sardinian Families

Summary. Our paper describes two Sardinian families with α‐β thalassaemia interaction. In the first (family S), the propositus, whose haemoglobin pattern at birth consisted of about 25% Hb Barts 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 β0 thalassaemia and heterozygous for α thalassaemia‐1 and α thalassaemia‐2. This conclusion is further substantiated by the finding of various combination of α and β thalassemia among his family members.

Prenatal Diagnosis of β Thalassaemia by Fetal Red Cell Enrichment with NH4Cl-NH4HCO3 Differential Lysis of Maternal Cells

Summary. Prenatal diagnosis with globin chain synthesis analysis on fetal red blood cells concentrated by NH4Cl‐NH2HCO3 differential lysis of maternal cells (Ørskov lysis) was carried out in 27 pregnancies at risk for β thalassaemia and one at risk for sickle cell β0 thalassaemia. The β/γ globin chain synthesis ratio was also determined after anti‐i differential agglutination (12 cases), in almost pure fetal samples (six cases) and by extrapolation (one case). Differential lysis permitted the study of samples drawn by placental aspiration containing as little as 3.2% fetal red blood cells. There was no consistent difference between the β/γ ratios observed after differential lysis and those determined after the use of the other approaches. A presumptive diagnosis of homozygous β thalassaemia was made in nine cases. All but one of these pregnancies was terminated. The absence of β chain synthesis was confirmed by the study of fetal blood after abortion in four cases with suitable samples. Of the remaining pregnancies, six proceeded to term and non‐homozygous infants were delivered. The others are still in progress. No fetal loss occurred. ørskov lysis seems to be a very reliable method for prenatal diagnosis of β chain abnormalities. Moreover it can minimize the number and duration of placental aspirations required and thus the risk to the fetus.

PRENATAL DIAGNOSIS OF β THALASSEMIA: EXPERIENCE WITH 133 CASES AND THE EFFECT OF FETAL BLOOD SAMPLING ON CHILD DEVELOPMENT *

Prenatal diagnosis was attempted in 133 pregnancies at risk for beta thalassemia (132 cases) or sickle-cell beta 0 thalassemia (1 case). Of these, 76 couples requested diagnosis because they already had children affected with homozygote beta thalassemia (72 cases) or beta+ thalassemia (4 cases). The others were probably at risk for beta 0 thalassemia since this is by far the predominant thalassemia type in Sardinia. Sufficient fetal blood for analysis was obtained by placental aspiration at 18--24 weeks gestation in 130 cases. Ten fetal losses occurred. The pregnancies were followed and no relevant complications were seen. Of the newborns delivered, 45 were followed from birth with particular attention to congenital malformation, neurological, growth, and maturity assessement. No major adverse effect of placentocentesis on child growth and development was observed. Placental samples were analyzed by globin chain synthesis analysis on carboxylmethylcellulose columns. When the placental samples contained more than 20% maternal red cells, fetal red cell enrichment was carried out by anti-i (53 cases) or anti-AB (2 cases) differential agglutination or NH4Cl-NH4HCO3 differential lysis of maternal cells (17 cases). Of the 130 cases, 32 fetuses had no beta-chain radioactivity and one had a beta/gamma ratio of 0.005. These were presumed to be homozygous and all but one were electively aborted. Absence of beta-chain radioactivity was confirmed in 10 abortuses with suitable cord blood samples. A total of 91 infants have been born and are nonhomozygous. Genotype assessment at 6 months after birth in 33 infants showed that there was only a slight overlap between the ranges of normal (0.095 +/- 0.016) and heterozygous (0.05 +/- 0.01) fetal beta/gamma globin chain synthesis ratios.

Hematological Characteristics of Sardinian α-Thalassemia Carriers Detected in a Population Study

88 adults with thalasseia-like red cell indices, normal serum iron and normal hemoglobin (Hb) A2 and F levels, diagnosed in a mass screening had Hb H inclusion bodies studies (65 subjects)

Diagnosis of the β0 Thalassemia Trait at Birth

This study shows the results of in vitro globin chain synthesis analysis in 33 infants who had been previously evaluated for the presence of thalassemia in the second trimester of gestation and were restudied after the stage of hematological maturity. Four children with α-thalassemia-1, identified in a newborn screening, were also included. Normals and β-thalassemia heterozygotes could be distinguished in the neonatal period by β/α or β/γ ratios. However, as a considerable overlap of α-thalassemia-1 with normals and α-thalassemia-2 with β-thal-assemia heterozygotes were found, biosynthetic studies at birth seem to be inappropriate to make reliable diagnosis of hemoglobin chain deficiences. There were no differences between hematological indices of normal and heterozygous β-thalassemia newborns, while α-thalassemia-l carriers showed a statistically significant difference from normals in mean MCV and MCH.