HBA1 – Hb Bart's Hydrops Fetalis

Hb Bart's hydrops fetalis is an autosomal recessive syndrome resulting from loss-of-function of both α-globin genes, including HBA1. Three unrelated fetuses carrying compound heterozygous α0-thalassemia deletions (–SEA/–GX and –SA/–SEA) involving HBA1 and HBA2 presented with early gestational hydrops (PMID:29493331; PMID:39286901; PMID:39526114).

Functional analyses attribute the phenotype to complete absence of α-globin chain synthesis, which abolishes embryonic haemoglobin Portland (ζ₂γ₂) formation and triggers severe fetal hydrops at early gestation (PMID:29493331). Prenatal ultrasound combined with comprehensive molecular screening for both common and rare α0-thalassemia deletions is essential for accurate diagnosis and management of this uniformly fatal condition.

Key Take-home: Expanded molecular testing of HBA1 alleles is critical to prevent undetected α0-thalassemia fetuses at risk for lethal hydrops.

References

• Hemoglobin • 2018 • Characterization of Hb Bart's Hydrops Fetalis Caused by –SEA and a Large Novel α0-Thalassemia Deletion. PMID:29493331
• Diagnosis (Berlin, Germany) • 2024 • Prenatal diagnostic errors in hemoglobin Bart's hydrops fetalis caused by rare genetic interactions of α-thalassemia PMID:39286901
• Practical laboratory medicine • 2024 • A novel case of Hb Bart's hydrops fetalis following prenatal diagnosis: Case report from Huizhou, China. PMID:39526114

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