Alpha_Thalassaemia_Flashcards
What causes alpha-thalassaemia?
Alpha-thalassaemia is caused by a deficiency of alpha chains in haemoglobin.
Where are the alpha-globulin genes located?
The alpha-globulin genes are located on chromosome 16.
How does the clinical severity of alpha-thalassaemia vary?
The clinical severity of alpha-thalassaemia depends on the number of alpha globulin alleles affected.
What is the blood picture if 1 or 2 alpha globulin alleles are affected?
If 1 or 2 alpha globulin alleles are affected, the blood picture would be hypochromic and microcytic, but the Hb level would typically be normal.
What happens if 3 alpha globulin alleles are affected?
If 3 alpha globulin alleles are affected, it results in hypochromic microcytic anaemia with splenomegaly.
What is the condition called when 3 alpha globulin alleles are affected?
The condition when 3 alpha globulin alleles are affected is known as Hb H disease.
What is the outcome if all 4 alpha globulin alleles are affected?
If all 4 alpha globulin alleles are affected, it results in death in utero (hydrops fetalis, Bart’s hydrops).
What is the condition called when all 4 alpha globulin alleles are affected?
The condition when all 4 alpha globulin alleles are affected is called hydrops fetalis or Bart’s hydrops.
summarise Alpha-thalassaemia
Alpha-thalassaemia
Alpha-thalassaemia is due to a deficiency of alpha chains in haemoglobin
Overview
2 separate alpha-globulin genes are located on each chromosome 16
Clinical severity depends on the number of alpha globulin alleles affected:
If 1 or 2 alpha globulin alleles are affected then the blood picture would be hypochromic and microcytic, but the Hb level would be typically normal
If are 3 alpha globulin alleles are affected results in a hypochromic microcytic anaemia with splenomegaly. This is known as Hb H disease
If all 4 alpha globulin alleles are affected (i.e. homozygote) then death in utero (hydrops fetalis, Bart’s hydrops)
Which one of the following is the most likely result if a fetus is homozygous for alpha-thalassaemia?
Anencephalic fetus
Normal pregnancy
Prematurity
Hydrops fetalis
Macrosomia
Hydrops fetalis
The correct answer is Hydrops fetalis. Alpha-thalassaemia is a blood disorder that reduces the production of haemoglobin. In its most severe form, known as alpha-thalassaemia major or hydrops fetalis, it results in fetal death in utero due to severe anaemia and heart failure. The fetus develops generalized oedema, known as hydrops. This occurs because the absence of alpha globin chains leads to an accumulation of excess beta globin chains which precipitate in red blood cells leading to their destruction (haemolysis) and hence severe anaemia.
The option Anencephalic fetus is incorrect. Anencephaly is a serious birth defect in which a baby is born without parts of the brain and skull. It is associated with a deficiency of folic acid intake during pregnancy but has no relation with alpha-thalassaemia.
Normal pregnancy would not be expected if a fetus was homozygous for alpha-thalassaemia, as this condition causes significant abnormalities including potentially fatal levels of anaemia.
The option Prematurity could be associated with many conditions but it’s not directly caused by being homozygous for alpha-thalassaemia. While complications related to thalassaemia may lead to preterm delivery, it’s not the direct result of the genetic condition itself.
Lastly, Macrosomia, which refers to a significantly larger-than-average newborn weight, is also not typically seen in cases of alpha-thalassaemia. It’s more commonly associated with maternal diabetes or obesity.
