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Postnatal changes in the quantities of globin chains and hemoglobin types in two babies with Hb H disease
1Department of Pediatrics, Medical College of Georgia, Augusta 30912-2100.
Insights
This study tracked two infants with Hemoglobin H disease, analyzing globin chain and hemoglobin changes. Lower fetal hemoglobin (Hb F) at birth helps reduce unstable Hemoglobin H (Hb H) but impairs oxygen transport.
Area of Science:
- Hematology
- Genetics
- Pediatrics
Background:
- Hemoglobin H (Hb H) disease is a genetic blood disorder.
- Understanding globin chain dynamics is crucial for managing Hb H disease.
- Newborns with Hb H disease exhibit specific hemoglobin profiles.
Purpose of the Study:
- To analyze changes in globin chains and hemoglobins in infants with Hb H disease from birth to six months.
- To correlate specific Hb H disease genotypes with globin chain levels.
- To evaluate the impact of hemoglobin composition on oxygen transport.
Main Methods:
- High-performance liquid chromatography (HPLC) was used to quantify globin chains (zeta, alpha, beta, G gamma, A gamma) and hemoglobins (Hb F, Hb A, Hb Bart's, Hb H).
- Two types of Hb H disease, -(SEA)/-alpha(3.7 kb) and -(Fil)/-alpha(3.7 kb), were studied.
- Globin chain and hemoglobin levels were monitored from birth to six months of age.
Main Results:
- Infants had functional hemoglobin (Hb A + Hb F) of 11-12 g/dl at birth, with 3-4 g/dl Hb Bart's and only 5% Hb H.
- Hb F levels were low (<50% of total Hb A+Hb F) at birth.
- Postnatal alpha and gamma chain production decreased, causing severe anemia (approx. 7 g/dl) at 30-60 days, improving to 8.5-9.5 g/dl by three months.
Conclusions:
- Preferential Hb A over Hb F formation at birth minimizes unstable Hb H levels.
- Low Hb F levels impair fetal blood's oxygen transfer capability.
- The -(Fil) deletion, encompassing the zeta 2-globin gene, explains higher zeta chain levels in one patient type.
Abstract:
We have studied two babies with Hb H disease from birth to about six months of age and analyzed the changes in the relative quantities of the five globin chains (zeta, alpha, beta, G gamma, A gamma) and the four hemoglobins (Hb F, Hb A, Hb Bart's, Hb H) using different high performance liquid chromatography procedures. The types of Hb H disease were -(SEA)/-alpha(3.7 kb) and -(Fil)/-alpha(3.7 kb); the larger -(Fil) deletion includes the functional zeta 2-globin gene, explaining the higher zeta chain level in the baby with the -(SEA)/-alpha(3.7 kb) type. The functional hemoglobin level at birth (Hb A+Hb F) was 11 to 12 g/dl with 3 to 4 g/dl Hb Bart's (gamma 4). Only 5% of the "fast-moving" hemoglobin was Hb H (beta 4). The level of Hb F at birth was low (less than 50% of the total Hb A+Hb F). After birth, the alpha and gamma chain production decreases rapidly resulting in a severe anemia (total functional hemoglobin approximately 7 g/dl) at 30 to 60 days postnatally, improving gradually to 8.5-9.5 g/dl at age of three months. The preferential formation of Hb A over Hb F at birth, and presumably prenatally, has the advantage that the level of the highly unstable Hb H is kept low; it also results in low levels of Hb F impairing the oxygen transfer capability of the fetal blood.