Hemoglobin Bart's hydrops fetalis syndrome (BHFS) is the most severe form of α-thalassemia, typically caused by homozygous deletion of α-globin genes. However, rare non-deletional variants, such as Hemoglobin (Hb) Agrinio, can also produce a lethal phenotype. We report a case of homozygous Hb Agrinio (HBA2:c.89T>C, p.Leu30Pro) diagnosed prenatally in a fetus of Bulgarian origin presenting with hydrops and severe anemia at 23 weeks of gestation. Following diagnosis, the pregnancy was managed with five intrauterine transfusions, resulting in resolution of hydrops and prolongation of pregnancy to term. The neonate was delivered at 37+3 weeks, required transient respiratory and cardiovascular support, and remains clinically stable at three months of age under regular transfusion therapy. To our knowledge, this is only the second reported case of BHFS resulting from homozygous Hb Agrinio successfully managed with intrauterine transfusions, and uniquely, the first to achieve term delivery. This case highlights the importance of considering unstable α-globin variants in the differential diagnosis of unexplained fetal hydrops in an at risk population. Early diagnosis and timely intrauterine transfusions can significantly improve the perinatal outcomes in these cases.

MCS-R regulatory elements are very important for the synthesis of α-globin. Deletion of the major α-globin regulatory elements compounded with deletion of α-globin genes can cause Hb Bart's (c4) hydrops fetalis, which is the severe form of α-thalassemia. In this report, a 19-year-old female at the 16th week of gestation came to our center due to abnormal fetal cardiothoracic ratio and thickened placental depth. The electrophoresis result of fetal umbilical cord blood revealed the level of Hb Bart's band to be 87.6%, which suggested the fetus was Hb Bart's hydrops fetalis. Next generation sequencing screen using targeted capture was used to detect the genotype of the fetus to be -SEA deletion, βA/βA. Multiplex ligation-dependent probe amplification (MLPA) is very useful to detect copy number variation (deletions/duplications), the result of which suggested the existence of -SEA deletion compounded with the novel large deletion of the major α-globin regulatory element (MCS-R2, R1, R3 and R4). Using the self-designed MLPA probe, the deletion should extend from the telomere downstream and the downstream breakpoint was between 143702 and 144291(GRch38/hg18). The novel deletion was also observed in the fetus' father and grandfather who had mild anemia. Of cases with the MCS deletion compounded with α0-thalassemia, this was the earliest time when the fetus presented fetal edema. Our study gave more evidence for genetic counseling for MCS deletion.

Hemoglobin Bart's hydrops fetalis is the most severe form of α-thalassemia, caused by homozygous α0-thalassemia, which is highly prevalent in Southeast Asian countries. Simple and rapid identification of α0-thalassemia carrier and prenatal diagnosis of Hemoglobin Bart's hydrops is essential in the region. We have developed a multiplex RPA assay for simple detection of α0-thalassemia (SEA and THAI deletions) and tested it in carrier detection (n = 125) and prenatal diagnosis of Hb Bart's hydrops fetalis syndrome (n = 30). The sensitivity, specificity, positive predictive value, and negative predictive value for detecting α0-thalassemia carriers were 100% for both SEA and THAI deletions. The assay correctly identified 42 carriers of α0-thalassemia (SEA deletion), 4 carriers of α0-thalassemia (THAI deletion), and 79 non-carriers. For prenatal diagnosis, the results of RPA revealed a 100% concordance (30/30) with the conventional gap-PCR analysis. The multiplex RPA assay is a rapid, reliable, and cost-effective method for diagnosing α0-thalassemia-related disorders in routine clinical settings. This assay has the potential to significantly contribute to the prevention and control of Hb Bart's hydrops fetalis in the region.

To describe rare genetic interactions of α-thalassemia alleles causing Hb H disease and Hb Bart's hydrops fetalis which could lead to diagnostic errors in a routine practice. Hematological and molecular characterization were carried out in a Thai family with a risk of having fetus with Hb Bart's hydrops fetalis. Both parents were found to be the thalassemia intermedia patients associated with unusual forms of Hb H disease. DNA analysis of common α-thalassemia mutations in Thailand identified α+-thalassemia (-α3.7 kb del) and unknown α0-thalassemia in the father and α0-thalassemia (--SEA) with unknown α+-thalassemia in the mother. Fetal DNA analysis unlikely identified a homozygosity for α0-thalassemia (--SEA/--SEA). Further analysis identified that the father carried a rare South African α0-thalassemia in combination with α+-thalassemia (--SA/-α), whereas the mother was a patient with Hb H-Queens Park disease (--SEA/ααQP). The fetus was, in fact, a compound heterozygote for (--SA/--SEA). As shown in this study, routine screening for α-thalassemia at prenatal diagnosis in the region should include both common and rare α0-thalassemia alleles found in the population to effectively prevent a fatal condition of Hb Bart's hydrops fetalis syndrome.

Hemoglobin Bart's hydrops fetalis syndrome (BHFS) represents the most severe form of α-thalassemia, arising from deletion of the duplicated α-globin genes from both alleles. The absence of α-globin leads to the formation of nonfunctional hemoglobin (Hb) Bart's (γ4) or HbH (β4) resulting in severe anemia, tissue hypoxia, and, in some cases, variable congenital or neurocognitive abnormalities. BHFS is the most common cause of hydrops fetalis in Southeast Asia; however, owing to global migration, the burden of this condition is increasing worldwide. With the availability of intensive perinatal care and intrauterine transfusions, an increasing number of patients survive with this condition. The current approach to long-term management of survivors involves regular blood transfusions and iron chelation, a task made challenging by the need for intensified transfusions to suppress the production of nonfunctional HbH-containing erythrocytes. Although our knowledge of outcomes of this condition is evolving, it seems, in comparison to individuals with transfusion-dependent β-thalassemia, those with BHFS may face an elevated risk of complications arising from chronic anemia and hypoxia, ongoing hemolysis, iron overload, and from their respective treatments. Although stem cell transplantation remains a viable option for a select few, it is not without potential side effects. Looking ahead, potential advancements in the form of genetic engineering and innovative therapeutic approaches, such as the reactivation of embryonic α-like globin gene expression, hold promise for furthering the treatment of this condition. Prevention remains a crucial aspect of care, particularly in areas with high prevalence or limited resources.