Alpha thalassemia Flashcards
How many alpha genes are there per cell?
4
Which chromosome are the alpha genes on?
chromosome 16
What are the types of heterozygous alpha trait?
loss of one of the chromosomes (3/4 remain)
fusion of one of the chromosomes (3/4 remain, one is fusion of both the genes from one chromosome)
Loss of both alpha genes on one chromosome (2/4 remain, both on same chromosome)
What are the types of homozygous states?
Loss of one alpha from both genes (2/4 remain)
Loss of all 4 genes (0/4 remain) - this is incompatible with life
What are the compound heterozygous states? What is it called?
Deletions of 3 alpha genes = A+, A0 on the other
HbH
What is the most common form of alpha thal?
-Alpha/-alpha
loss of one on each
What is the effect of alpha thalassemia trait on life?
It is harmless
No problems, implications only arise if they want to have a child with another alpha thal trait
Describe the red cell indicies seen in alpha thal trait.
Low Hb ,MCV and MCH<25
What occurs in HbH?
Moderatey sever hypochromic microcytic anaemia
Excess Beta chains form an abnormal hb with 4 b chain tetramers - HbH
What is seen in HbH and why?
Splenomegaly
HbHs precipitate and cause intra and extravascular haemolysis
How is HbH diagnosed?
Red cell index and film
HPLC
Electrophoresis
What distinctive cell is seen in the film of HbH?
Golf ball cells
Raised retics
What are the globin chains seen in hydrops fetalis?
no normal HbA
only HbGower and Portland seen
Which parents are at risk of hydrops baby?
Those with both alpha globin from one gene
