Haemoglobin Bart's hydrops syndrome

Haemoglobin Bart's hydrops syndrome occurs in the homozygous state for alpha0 thalassaemia, genotype --/-- (1).

• it is inherited if both parents are carriers for the deletion of two α-globin genes in cis on one chromosome 16
• there is a 1 in 4 chance of baby being born with this condition (1).
• because of the α-globin chains are needed during gestation the fetus would develop severe anemia, and hypoxia, heart failure, and hydrops fetalis (1).

The complete absence of alpha chains leads to an excess of gamma chains which forms gamma tetramers or haemoglobin Bart's (γ4) (1). This has a very high oxygen affinity and therefore is physiologically useless.

These foetuses have severe anaemia due to defective haemoglobin production (1). At birth the new borns are pale, large and oedematous with features of anasarca, congenital abnormalities, limb reduction defects and high output cardiac failure (1).

Enormously hypertrophied placentas make the birth of these stillborn foetuses extremely difficult and there is also a high incidence of maternal toxaemia of pregnancy and half these mothers would die if there is no medical intervention (1).

The affected fetus will die in the third trimester of gestation or hours within birth and medical intervention is aimed at identifying couples at risk, counseling them and prenatal diagnosis during early pregnancy. Screening involves blood counts and hemoglobin electrophoresis (1).

If detected late in the pregnancy the main concern is maternal wellbeing (1).

There are cases of survival of newborns that have been transfused immediately post delivery or received intrauterine transfusions and treated like β thalassaemia major with regular blood transfusions. These children have serious neonatal complications and some congenital abnormalities (1).

Reference:

• (1) David H.K. Chui and John S. Waye, S, 1998. Hydrops Fetalis Caused by α-Thalassemia: An Emerging Health Care Problem. Blood, 91 (7), 2213-2222