Bart's hydrops fetalis--clinical presentation and management--an analysis of 25 cases

Αlpha-thalassemia: A practical overview

α-Thalassemia is an inherited blood disorder characterized by decreased synthesis of α-globin chains that results in an imbalance of α and β globin and thus varying degrees of ineffective erythropoiesis, decreased red blood cell (RBC) survival, chronic hemolytic anemia, and subsequent comorbidities. Clinical presentation varies depending on the genotype, ranging from a silent or mild carrier state to severe, transfusion-dependent or lethal disease. Management of patients with α-thalassemia is primarily supportive, addressing either symptoms (eg, RBC transfusions for anemia), complications of the disease, or its transfusion-dependence (eg, chelation therapy for iron overload). Several novel therapies are also in development, including curative gene manipulation techniques and disease modifying agents that target ineffective erythropoiesis and chronic hemolytic anemia. This review of α-thalassemia and its various manifestations provides practical information for clinicians who practice beyond those regions where it is found with high frequency.

The role of molecular diagnostic testing for hemoglobinopathies and thalassemias

Hemoglobin disorders are among the most common genetic diseases worldwide. Molecular diagnosis is helpful in cases where the diagnosis is uncertain and for genetic counseling. Protein-based diagnostic techniques are frequently adequate for initial diagnosis. Molecular genetic testing is pursued in some cases, particularly when a definitive diagnosis is not possible and especially for the purpose of assessing genetic risk for couples wanting to have children. The expertise available in the clinical hematology laboratory is essential for the diagnosis of patients with hemoglobin abnormalities. Initial diagnoses are made using protein-based techniques such as electrophoresis and chromatography. Based on these findings, genetic risk to an individual's offspring can be assessed. In the setting of β-thalassemia and other β-globin disorders, coincident α-thalassemia may be difficult to diagnose, which can have potentially serious consequences. In addition, unusual forms of β-thalassemia caused by deletions in the β-globin locus cannot be definitively characterized using standard techniques. Molecular diagnostic testing has an important role in the diagnosis of hemoglobin disorders and is important in the setting of genetic counseling. Molecular testing also has a role in prenatal diagnosis to identify fetuses affected by severe hemoglobinopathies and thalassemias.

A Rare Case of Hemoglobin Bart's Hydrops Fetalis due to Uniparental Disomy of Chromosome 16

Hemoglobin (Hb) Bart’s hydrops fetalis is the most severe form of α-thalassemia and is usually inherited in an autosomal recessive manner. We report a case of Hb Bart’s hydrops fetalis due to uniparental disomy of chromosome 16. Antenatal screening showed a low maternal mean corpuscular volume (MCV), while paternal MCV was normal. The fetus was found to have a thickened nuchal translucency during first trimester screening for Down’s syndrome. Mid-trimester fetal anomaly ultrasound scan showed fetal cardiomegaly with pericardial effusion, scalp edema, ascites and an elevated middle cerebral arterial peak systolic velocity (MCA PSV). Multiplex polymerase chain reaction (PCR) on DNA from amniocentesis showed that the fetus was homozygous for South East Asian (SEA) type 2 α-globin gene deletion. Chromosome microarray (CMA) showed two regions of absence of heterozygosity (AOH) on the terminal p and q arm of chromosome 16. The rare occurrence of Hb Bart’s hydrops fetalis caused by maternal uniparental disomy should be considered in cases of fetal hydrops even in cases where paternal MCV is normal.

Forager and farmer evolutionary adaptations to malaria evidenced by 7000 years of thalassemia in Southeast Asia

Thalassemias are inherited blood disorders that are found in high prevalences in the Mediterranean, Southeast Asia and the Pacific. These diseases provide varying levels of resistance to malaria and are proposed to have emerged as an adaptive response to malaria in these regions. The transition to agriculture in the Holocene has been suggested to have influenced the selection for thalassemia in the Mediterranean as land clearance for farming encouraged interaction between Anopheles mosquitos, the vectors for malaria, and human groups. Here we document macroscopic and microscopic skeletal evidence for the presence of thalassemia in both hunter-gatherer (Con Co Ngua) and early agricultural (Man Bac) populations in northern Vietnam. Firstly, our findings demonstrate that thalassemia emerged prior to the transition to agriculture in Mainland Southeast Asia, from at least the early seventh millennium BP, contradicting a long-held assumption that agriculture was the main driver for an increase in malaria in Southeast Asia. Secondly, we describe evidence for significant malarial burden in the region during early agriculture. We argue that the introduction of farming into the region was not the initial driver of the selection for thalassemia, as it may have been in other regions of the world.

Molecular Diagnosis of Thalassemias and Hemoglobinopathies: An ACLPS Critical Review

OBJECTIVES

To describe the use of molecular diagnostic techniques for patients with hemoglobin disorders.

METHODS

A clinical scenario is presented in which molecular diagnosis is important for genetic counseling. Globin disorders, techniques for their diagnosis, and the role of molecular genetic testing in managing patients with these disorders are described in detail.

RESULTS

Hemoglobin disorders, including thalassemias and hemoglobinopathies, are among the commonest genetic diseases, and the clinical laboratory is essential for the diagnosis of patients with these abnormalities. Most disorders can be diagnosed with protein-based techniques such as electrophoresis and chromatography. Since severe syndromes can result due to inheritance of combinations of globin genetic disorders, genetic counseling is important to prevent adverse outcomes. Protein-based methods cannot always detect potentially serious thalassemia disorders; in particular, α-thalassemia may be masked in the presence of β-thalassemia. Deletional forms of β-thalassemia are also sometimes difficult to diagnose definitively with standard methods.

CONCLUSIONS

Molecular genetic testing serves an important role in identifying individuals carrying thalassemia traits that can cause adverse outcomes in offspring. Furthermore, prenatal genetic testing can identify fetuses with severe globin phenotypes.

Prenatal control of Hb Bart's disease in mainland China: can we do better?

The aim of the present study was to report a 3-year experience on the prenatal control of Hb Bart's (γ4) disease in Mainland China. All pregnancies with fetal Hb Bart's disease were included from January 2011 to December 2013. The main clinical characteristics of the affected pregnancies were reviewed, including maternal reproductive history, prenatal care in the current pregnancy, the gestation of pregnancy at the time of booking, the gestation at the time of prenatal diagnosis (PND), and the complications associated with the pregnancy. A total of 246 cases of fetal Hb Bart's disease were identified during the study period; among these, 177 (72.0%) were diagnosed in early gestation (≤24 weeks), and 69 (28.0%) in late gestation. Most (87.0%) of the patients presenting in late pregnancy had late or no prenatal care. Twenty (29.0%) had major obstetrical complications in patients presenting in late pregnancy, and five (5.0%) in patients presenting in relatively early pregnancy. The delay in PND deprived couples of opportunities to make informed decisions early in pregnancy. Efforts for designing and targeting strategies to improve the timeliness of prenatal care are urgently needed.

Homozygous alpha-thalassemia in a growth retarded, non-hydropic premature newborn

A newborn with homozygous alpha-thalassemia presented with intrauterine growth retardation and presumed persistent pulmonary hypertension. He also had moderate anemia, hepatomegaly and hypospadias. Correlating the newborn's clinical presentation with an underlying cause of anemia was helpful for early diagnosis. Prenatal blood tests must include red cell indices and a mean corpuscular volume value below 80 fL should prompt thalassemia screening in an at-risk population.

Spontaneous antenatal resolution of canine hydrops fetalis diagnosed by ultrasound

A previously unreported syndrome of transient mid-gestational hydrops fetalis identified by ultrasound was diagnosed in 16 litters of 16 different dogs between November 1999 and May 2002. During this study period, a total of 161 canine pregnancies were diagnosed by ultrasound. A 17th litter of eight fetuses developed similar ultrasonographic changes concurrently with maternal systemic mastocytosis and subsequently spontaneously aborted. No pups were born with clinical signs of hydrops fetalis. Fetal resorption in the affected litters was 7/95 (7.4 per cent) and 8/95 (8.4 per cent) aborted. Of the fetuses that survived to term, there were 7/88 (8 per cent) stillbirths. Neonatal mortality rate in the affected litters was 15 per cent (11/73) and the incidence of congenital abnormalities was 7/73 (9.6 per cent). Pugs were significantly (22.8 times) more likely to be affected than other breeds.

Real-time quantitative PCR analysis for alpha-thalassemia-1 of Southeast Asian type deletion in Taiwan

Since homozygosity of the alpha-thalassemia-1 of Southeast Asian (SEA) type deletion results in hydrops fetalis, a novel protocol based on the real-time quantitating polymerase chain reaction (PCR) technique has been developed to quantify the intact and aberrant alpha-globin genes in adults. The ratio of the normal/SEA-bearing alpha-globin genes was expressed in cycle threshold (C(T)) values. Theoretically, a relative ratio of one to one was anticipated in individuals carrying the SEA type deletion. Twenty-five heterozygous and 20 normal cases were analyzed retrospectively with this protocol. Data showed that the CT values for the intact alpha-globin gene allele and the allele bearing the SEA type deletion in carriers were 28.74+/-1.49 and 26.46+/-2.05, respectively. Therefore, the ratio of normal/SEA type deletion-bearing alpha-globin genes in the carriers was 1.09+/-0.043. No ambiguous results were observed from other less common genotypes associated with alpha-thalassemia, such as the Philippine type deletion. Based on the results, we concluded that this protocol could provide a rapid method to mass screen carriers with alpha-thalassemia-1 of SEA type deletion in this region.

Second-trimester hydrops fetalis in pregnancies affected by homozygous alpha-thalassaemia-1

Homozygous alpha-thalassaemia-1 is the commonest cause of hydrops fetalis in South-East Asia. Ultrasonographic features of hydrops fetalis were said to be evident only after 20 weeks of gestation. We studied 111 pregnancies at risk of homozygous alpha-thalassaemia-1 at 12-14 gestational weeks and 101 pregnancies at 17-18 weeks by abdominal ultrasound examination. Ultrasonographic features of hydrops fetalis were seen in 3 out of 44 pregnancies affected by homozygous alpha-thalassaemia-1 at 12-14 weeks [7 per cent; 95 per cent confidence interval (CI) 1-19 per cent] and in 7 out of 21 affected pregnancies at 17-18 weeks (33 per cent; 95 per cent CI 15-57 per cent). In conclusion, homozygous alpha-thalassaemia-1 can cause hydrops fetalis in the early second trimester. It should constitute one of the differential diagnoses in the work-up of second-trimester hydrops fetalis.