Alpha Thalassemia Flashcards
What is alpha thalassemia?
In alpha-thalassemia, one or more structural genes are physically absent from the genome
What does it mean to be a silent carrier for alpha thalassemia?
A single gene deletion (alpha-thalassemia-2) is clinically undetectable and is called the silent carrier state.
***only one of the four genes is missing
What is alpha thalassemia minor?
2 of the 4 genes are missing.
In blacks, the most common two-gene deletion state consists of one gene missing on each chromosome (trans). In Asians, most often both genes are missing from the same chromosome (cis).
What is hemoglobin H disease?
3 of the 4 genes are missing.
Hb H (beta globulin x 4)
Hb H precipitates in the RBC, the cell is removed by the reticuloendothelial system, leading to a moderately severe hemolytic anemia.
What is hemoglobin Barts?
4 of 4 genes are missing.
Barts (gamma globulin x 4)
Hydrops fetalis
How is alpha thalassemia inherited?
Autosomal recessive
Barts require 2 alpha thalassemia-1 (minor) in the cis position
What is microcytic anemia?
MCV less than 75-80
How do you diagnose microcytic anemia?
CBC
What is your differential diagnosis for microcytic anemia?
Lead poisoning Sideroblastic anemia Thalassemia Iron deficiency anemia Anemia of chronic disease (late onset)
What are the fetal risks with alpha thalassemia?
- Cardiac failure
- Hydrops fetalis
- Still birth
- IUGR
Why does hydrops develop in fetuses with hemoglobin Barts?
the fetus is unable to synthesize normal Hb F or any adult hemoglobins.
This deficiency results in high-output cardiac failure, hydrops fetalis, and stillbirth.
Why is hemoglobin Barts more likely to develop in fetuses of Asian ancestry?
Cis configuration of the missing 2 genes.
How do you screen for alpha thalassemia?
Screening is by dx of exclusion with microcytic anemia (test for alpha thalassemia with PCR if microcytic anemia and no iron deficiency and no beta thalassemia on hemoglobin electrophoresis)
What would you expect to see on electrophoresis for alpha thalassemia?
it would be normal
What are pregnancy risks for patients with alpha thalassemia?
The course of pregnancy in women with the α-thalassemia trait is not significantly different from that of women with normal hemoglobin. Pregnancy in women with Hb H disease has been reported, and with the exception of mild to moderate chronic anemia, outcomes have been favorable
