Long-term survival of a baby with homozygous alpha-thalassemia-1

An international registry of survivors with Hb Bart's hydrops fetalis syndrome

Hemoglobin (Hb) Bart's hydrops fetalis syndrome (BHFS) resulting from α0-thalassemia is considered a universally fatal disorder. However, over the last 3 decades, improvements in intrauterine interventions and perinatal intensive care have resulted in increasing numbers of BHFS survivors. We have initiated an international registry containing information on 69 patients, of which 31 are previously unpublished. In this perspective, we analyze the available clinical information to document the natural history of BHFS. In the future, once we have accrued sufficient cases, we aim to build on this study and provide information to allow counseling of at-risk couples. To date, 39 patients have survived beyond the age of 5 years, 18 of whom are now older than 10 years. Based on the available cases, we find evidence to suggest that intrauterine therapy provides benefits during the perinatal and neonatal period; however, it may not provide additional benefits to long-term growth and neurodevelopmental outcomes. Growth retardation is a major adverse long-term outcome among BHFS patients with ∼40% being severely affected in terms of weight and ∼50% in terms of height. There is also an increased risk of neurodevelopmental delay as we find 20% (11/55) of BHFS survivors suffer from a serious delay of ≥6 months. Most patients in the registry require lifelong transfusion and often have associated congenital abnormalities and comorbidities. This perspective is a first step in gathering information to allow provision of informed counseling on the predicted outcomes of affected babies.

Pulmonary hypoplasia and persistent pulmonary hypertension in the newborn with homozygous α-thalassemia: a case report and review of the literature

The survival of infants with homozygous alpha-thalassemia, once considered a lethal diagnosis, is now possible through in utero and postnatal diagnostic and therapeutic interventions. We report the survival of a newborn with homozygous alpha-thalassemia complicated by pulmonary hypoplasia and persistent pulmonary hypertension, an association not previously reported.

Alpha-thalassaemia

Alpha-thalassaemia is one of the most common human genetic disorders. Couples in which both partners carry alpha(0)-thalassaemia traits have a 25% risk of having a fetus affected by homozygous alpha-thalassaemia or haemoglobin Bart's disease, with severe fetal anaemia in utero, hydrops fetalis, stillbirth or early neonatal death, as well as causing various maternal morbidities. This disorder is common in southeast Asia and southern China, and the expanding populations of southeast Asian immigrants in the US, Canada, UK and Europe mean that this disorder is no longer rare in these countries.

Outcome of intensive care of homozygous alpha-thalassaemia without prior intra-uterine therapy

AIM

To review the outcome of homozygous alpha-thalassaemia without prior intra-uterine therapy treated in neonatal intensive care unit and identify the factors associated with survival.

METHODS

The hospital records of all patients with homozygous alpha-thalassaemia treated in our neonatal intensive care unit in the last 15 years were reviewed. A literature search beginning in the year 1980 was done to identify homozygous alpha-thalassaemia actively treated in neonatal intensive care units. Those receiving prior intra-uterine therapy were excluded. The following information was collected: the severity of hydrops, sizes of liver and spleen, haemoglobin level, Apgar score at 5 min, ventilator settings, timing and forms of red blood cell transfusion and presence of persistent hypoxaemia. The survivors and the non-survivors were compared.

RESULTS

In our centre, in the last 15 years there were six infants born with homozygous alpha-thalassaemia who did not receive intra-uterine therapy; one survived and five succumbed despite aggressive respiratory therapy. In our literature search there were more reports of survivors (10) than non-survivors (six) for these infants, suggesting a reporting bias towards selection of rare cases of survival. Apgar score of four or above occurred in seven of the eight survivors with data available in the reports, whereas this occurred in four of the 11 non-survivors (P = 0.035, Fisher Exact test). Five of the 11 survivors had abnormal neurological outcome including developmental delay and spastic quadriplegia.

CONCLUSION

Without prior intra-uterine therapy, homozygous alpha-thalassaemia has grave outlook in terms of mortality and morbidity despite aggressive respiratory therapy.

Neurodevelopmental outcome and haematological course of a long-time survivor with homozygous alpha-thalassaemia: case report and review of the literature

AIM

Homozygous alpha-thalassaemia, also called haemoglobin (Hb) Bart's hydrops fetalis, has been thought to be a lethal condition. Due to prenatal diagnosis and intrauterine blood transfusions, a few patients with Hb Bart's hydrops fetalis have survived. This fact raises the urgent questions of clinical management and appropriate follow-up of these patients, both of which are addressed in this article.

METHODS

We report on a 6.5-y-old patient with homozygous alpha-thalassaemia and review the literature of 13 other survivors published to date. Transfusion requirements were evaluated and the rate of liver iron accumulation was assessed by biomagnetic liver susceptometry before and after institution of iron-chelating therapy. Psychometric evaluation was carried out using Munich's Functional Development Test, the Columbia Mental Maturity Scale, the Kaufman Assessment Battery for Children, and the Peabody Picture Vocabulary Test.

RESULTS

Our patient had significant delay of psychomotor development. Psychometric evaluation at the age of 5 y revealed an IQ of 85 and an intellectual level of a 4-y-old child. Early tissue iron overload was seen, but a negative iron balance was achieved after institution of desferrioxamine treatment at dosages used for beta-thalassaemia.

CONCLUSION

Homozygous alpha-thalassaemia should no longer be regarded as a lethal condition. Early intervention during pregnancy and careful haematological as well as neuropsychological follow-up was able to provide long-term survival and good life quality in our patient.

Vascular-type disruptive defects in fetuses with homozygous α-thalassemia: report of two cases and review of the literature

BACKGROUND

The thalassemias are an inherited group of heterogeneous anemias in which one or more of the globin chains in the hemoglobin tetramer are absent. Fetuses with homozygous alpha-thalassemia, which is particularly prevalent in people of Southeast Asian extraction, experience deficient alpha-globin chain synthesis and cannot produce hemoglobin F (the primary fetal hemoglobin after 8 weeks' gestation). Instead, they produce an anomalous hemoglobin, hemoglobin Bart's, with an unusually high affinity for oxygen, leading to profound anemia and tissue hypoxia.

METHODS AND RESULTS

Here we report on two fetuses with homozygous alpha-thalassemia who displayed structural defects of a vascular disruptive type. Both fetuses demonstrated limb anomalies, including terminal transverse limb deficiencies, and one fetus was found to have a brain malformation consisting of a neuronal migrational defect. The limb anomalies and suspected brain malformation were detected on prenatal ultrasound prior to confirmation of the diagnosis of alpha-thalassemia in one case; in the other case prenatal records were not available. While microcephaly, hydrocephalus, and retarded brain growth have been rarely reported in association with homozygous alpha-thalassemia, this is the first report of a true brain malformation in an affected fetus. Limb anomalies, on the other hand, appear to be more frequent. Recently, aggressive in utero and postnatal therapies for homozygous alpha-thalassemia have been attempted with some success.

CONCLUSIONS

Our cases and those from the medical literature suggest that couples need to be counseled about the risks of congenital anomalies of a vascular disruptive type in affected fetuses. Furthermore, data from the literature suggests that in utero therapy may not significantly decrease these risks as such anomalies may be present prior to the institution of therapy. In addition, in hydropic infants with vascular disruptive defects, especially in those of Southeast Asian origin, homozygous alpha-thalassemia should be suspected as a likely etiology.

Testing for hematologic disorders and complications

This review summarizes state-of-the-art and emerging techniques in the antenatal diagnosis of fetal anemia and hemoglobinopathies. Fetal anemia may result from hemolytic disease, hemorrhage, suppression of erythropoiesis, infection (eg, parvovirus B19), or trauma. The clinical laboratory plays an essential role in the evaluation of these disorders by way of the use of various hematologic, biochemical, serologic, cytometric, and molecular genetics methods. Hemoglobinopathies are the most common class of single gene disorders worldwide. The authors have used the example of homozygous alpha-thalassemia major (Hb Barts disease) as a paradigmatic case for antenatal hemoglobinopathy screening. Perhaps the most familiar indication for hematologic screening in pregnancy is HDFN, most commonly in pregnancies previously sensitized to the RhD antigen. All pregnant women, regardless of their past medical or obstetric history or previous antibody screens, should have ABO/Rh blood typing and a red cell antibody screen performed at the first prenatal visit. Long-established methods for assaying FMH (KB method), microcytosis (hemogram with red cell indices), and blood group incompatibility (direct antigen test, serologies) remain critical for rapid, sensitive diagnosis. Analysis of fetal free DNA in maternal plasma holds the promise for rapid, ultrasensitive, and noninvasive detection of many fetal hematologic disorders.

Changing outcome of homozygous alpha-thalassemia: cautious optimism

Only a few long-term survivors of homozygous alpha-thalassemia, a usually fatal condition, have been reported. The authors present a surviving infant with this disorder and discuss the complications, treatments, and implications of this genetic hemoglobinopathy. The child had no antenatal intervention and has been treated with regular transfusions. She has had normal growth and development and is currently 2.5-years-old. A literature review of survivors with Bart hemoglobinopathy reveals an intense perinatal course and a great prevalence of congenital urogenital and limb defects. Advances in antenatal diagnosis, intrauterine intervention, and postnatal treatments have resulted in extended survival of children with congenital defects that until recently were considered invariably fatal. Transfusion and chelation therapy and bone marrow transplantation provide long-term treatment and potential curative options.

Ten years' experience of antenatal mean corpuscular volume screening and prenatal diagnosis for thalassaemias in Hong Kong

OBJECTIVE

To determine the prevalence of thalassaemia carriers in Hong Kong.

SUBJECTS AND METHODS

From 1988 to 1997, 25,834 (53.7%) of 48,089 mothers were screened for thalassaemias by mean corpuscular volume (MCV) at the first antenatal visit.

RESULTS

In the screened population of 25,834, 2229 (8.6%) had MCV < or = 75 fl. Of these, 1121 (4.3%) were alpha-thal, 715 (2.8%) were beta-thal, 23 (0.1%) were alpha beta-thal, 57 (0.2%) were other haemoglobin variants, and 281 (1.1%) had either iron deficiency or uncertain causes. Out of 200 pregnancies at risk for homozygous alpha-thal-1 and 32 at risk for beta-thal major, 27 homozygous alpha-thal-1 and 7 beta-thal major were identified, compared favourably with the expected figures of 23 and 9.

CONCLUSION

Antenatal screening for thalassaemias by MCV is simple, effective and reliable. Universal screening has a different impact as bone marrow or cord blood stem cell transplant provides cure for beta-thal major. At risk couples have, as an alternative to termination of pregnancy, the option of early detection and treatment for their affected newborns or fetuses.

Treatment of hemoglobin Bart's hydrops with bone marrow transplantation

A 21-month-old girl with hemoglobin Bart's hydrops received bone marrow transplantation (BMT) from a matched sibling. No major BMT-related complications developed. Hemoglobin levels remained greater than 10 gm/dl for 20 months without blood transfusion support despite the presence of residual host hemopoietic cells from 2 months after BMT. We suggest consideration of this therapeutic option for surviving patients.

Alpha-thalassaemia

alpha-Thalassaemias are genetic defects extremely frequent in some populations and are characterized by the decrease or complete suppression of alpha-globin polypeptide chains. The gene cluster, which codes for and controls the production of these polypeptides, maps near the telomere of the short arm of chromosome 16, within a G + C rich and early-replicating DNA region. The genes expressed during the embryonic (zeta) or fetal and adult stage (alpha 2 and alpha 1) can be modified by point mutations which affect either the processing-translation of mRNA or make the polypeptide chains extremely unstable. Much more frequent are the deletions of variable size (from approximately 3 to more than 100 kb) which remove one or both alpha genes in cis or even the whole gene cluster. Deletions of a single gene are the result of unequal pairing during meiosis, followed by reciprocal recombination. These unequal cross-overs, which produce also alpha gene triplications and quadruplications, are made possible by the high degree of homology of the two alpha genes and of their flanking sequences. Other deletions involving one or more genes are due to recombinations which have taken place within non-homologous regions (illegitimate recombinations) or in DNA segments whose homology is limited to very short sequences. Particularly interesting are the deletions which eliminate large DNA areas 5' of zeta or of both alpha genes. These deletions do not include the structural genes but, nevertheless, suppress completely their expression. Larger deletions involving the tip of the short arm of chromosome 16 by truncation, interstitial deletions or translocations result in the contiguous gene syndrome ATR-16. In this complex syndrome alpha-thalassaemia is accompanied by mental retardation and variable dismorphic features. The study of mutations of the 5' upstream flanking region has led to the discovery of a DNA sequence, localized 40 kb upstream of the zeta-globin gene, which controls the expression of the alpha genes (alpha major regulatory element or HS-40). In the acquired variant of haemoglobin H (HbH) disease found in rare individuals with myelodysplastic disorders and in the X-linked mental retardation associated with alpha-thalassaemia, a profound reduction or absence of alpha gene expression has been observed, which is not accompanied by structural alterations of the coding or controlling regions of the alpha gene complex. Most probably the acquired alpha-thalassaemia is due to the lack of soluble activators (or presence of repressors) which act in trans and affect the expression of the homologous clusters and are coded by genes not (closely) linked to the alpha genes. The ATR-X syndrome results from mutations of the XH2 gene, located on the X chromosome (Xq13.3) and coding for a transacting factor which regulates gene expression. The interaction of the different alpha-thalassaemia determinants results in three phenotypes: the alpha-thalassaemic trait, clinically silent and presenting only limited alterations of haematological parameters, HbH disease, characterized by the development of a haemolytic anaemia of variable degree, and the (lethal) Hb Bart's hydrops fetalis syndrome. The diagnosis of alpha-thalassaemia due to deletions is implemented by the electrophoretic analysis of genomic DNA digested with restriction enzymes and hybridized with specific molecular probes. Recently polymerase chain reaction (PCR) based strategies have replaced the Southern blotting methodology. The straightforward identification of point mutations is carried out by the specific amplification of the alpha 2 or alpha 1 gene by PCR followed by the localization and identification of the mutation with a variety of screening systems (denaturing gradient gel electrophoresis (DGGE), single strand conformation polymorphisms (SSCP)) and direct sequencing.

The use of a highly informative CA repeat polymorphism within the abetalipoproteinaemia locus (4q22-24)

Abetalipoproteinaemia is a rare autosomal-recessive disorder caused by a defect in the large subunit of the microsomal triglyceride transfer protein (MTP) which is required for the assembly and secretion of apolipoprotein B-containing lipoproteins. We report here the use of a polymorphic CA dinucleotide repeat in intron 10, MTPIVS10, of the large subunit of the human MTP protein in the analysis of a pregnancy in a consanguineous family, in which abetalipoproteinaemia was suspected, although prenatal diagnosis was subsequently refused. The mutation in the family has been identified as a novel four-nucleotide insertion/duplication of exon 17 between nucleotides 2349 and 2350 of the cDNA sequence of the MTP gene. However, the marker, MTPIVS10, can be used as an alternative to the time-consuming mutation detection techniques.

Fetal erythropoiesis and the diagnosis and treatment of hemoglobin disorders in the fetus and child

Although synthesis of adult hemoglobin (alpha 2 beta 2) is reduced or absent in both alpha and beta thalassemias, these disorders differ in their clinical significance to the fetus and neonate. alpha-Globin synthesis is observed in the yolk sac by 3 weeks of gestation and, by 9 weeks of gestation, alpha-globin represents the main alpha-like hemoglobin in the fetus. By contrast, the switch to beta-globin chain synthesis usually remains incomplete until 1 year after birth. Therefore, the clinical manifestations of homozygous beta-thalassemia may be ameliorated by sustained synthesis of fetal hemoglobin during the first 6 months of life, whereas up until 10 years ago, homozygous alpha-thalassemia was invariably associated with death in utero. More recently, reports of infants with homozygous alpha-thalassemia surviving the neonatal period have emerged, observations particularly relevant to large numbers of immigrants to North America from Southeast Asia, where alpha-thalassemia is common. Studies of patients with the beta-globin disorders thalassemia and sickle cell disease showed that the severity of both disorders is ameliorated by sustained synthesis of fetal hemoglobin into adult life. Hence, treatment for both these disorders has focused on the pharmacological manipulation of fetal hemoglobin. Studies in vitro, in animal models, and in affected patients have shown that several compounds stimulate gamma-globin synthesis and fetal hemoglobin production through a variety of proposed mechanisms. Some of the successes in human trials are outlined herein.

Limb defects and congenital anomalies of the genitalia in an infant with homozygous alpha-thalassemia

We describe an infant with homozygous alpha-thalassemia, genital abnormalities, and terminal transverse limb defects, whose limbs demonstrate evidence of loss of tissue and abnormal morphogenesis. We propose these defects were due to either severe fetal anemia or to vascular occlusion by abnormal erythrocytes, resulting in hypoxia of the developing distal limbs and genitalia.

Limb defects in homozygous alpha-thalassemia: report of three cases

Homozygosity for the South-Asian alpha-thalassemia (--SEA/) deletion is a serious hematological condition that results, in most cases, in intrauterine or postnatal death due to anemia and severe hypoxia of prenatal onset. A relationship between congenital abnormalities and intra-uterine hypoxia has been postulated. However, since homozygosity for the (--SEA/) deletion is most common in underdeveloped countries where detailed autopsies are lacking, the incidence of congenital abnormalities among these babies has not been well delineated. We report on three newborn infants, homozygous for the (--SEA/) deletion, who were born with limb defects. We postulate that this combination is the result of prenatal hypoxia which may affect other fetal body organs. This should be taken into consideration when prenatal treatment of affected fetuses, with intrauterine blood transfusion, is suggested.

Lethal alpha-thalassaemia created by gene targeting in mice and its genetic rescue

Mutations at the alpha-globin locus are the most common class of mutations in humans, with deletion of all four adult alpha-globin genes resulting in the perinatal lethal condition haemoglobin Barts hydrops fetalis. Using gene targeting in mice, we have deleted a 16 kilobase region encompassing both adult alpha-globin genes. Animals homozygous for this deletion become hydropic and die late in gestation mimicking humans with hydrops fetalis. Introduction of a human alpha-globin transgene rescued these animals from perinatal death thus demonstrating the utility of this murine model in the development of cellular and gene based approaches for treating this human genetic disease.