hemoglobin Bart's
Abnormal hemoglobin composed of four gamma chains, indicating severe alpha-thalassemia and associated with hydrops fetalis.
Full Definition
Hemoglobin Bart's (Hb Bart's) is an abnormal hemoglobin variant composed entirely of gamma globin chains (γ4) that forms when alpha globin chain production is severely reduced or absent. This hemoglobin has an extremely high oxygen affinity and cannot effectively deliver oxygen to tissues. Hemoglobin Bart's is characteristic of the most severe form of alpha-thalassemia (Hb Bart's hydrops fetalis syndrome), which occurs when all four alpha globin genes are deleted or non-functional. Affected fetuses typically develop severe anemia, hydrops fetalis, and usually die in utero or shortly after birth. The presence of Hb Bart's in newborn screening indicates alpha-thalassemia carrier status in milder cases.
Usage
Usage note: Capitalize 'Bart's' as it refers to St. Bartholomew's Hospital where first described.
In Context
- "Hemoglobin electrophoresis revealed 80% hemoglobin Bart's, consistent with the diagnosis of Hb Bart's hydrops fetalis syndrome." — Prenatal diagnostic report
- "The presence of 5% hemoglobin Bart's on newborn screening suggested alpha-thalassemia trait in this Southeast Asian infant." — Newborn screening follow-up