Haemoglobinopathies Flashcards
what chromosome are alpha genes found on?
16
(2 per chromosome)
what chromsome are beta genes found on?
11
(1 per chromosome)
at what age are adult levels of Hb achieved?
6-12 months
how can haemoglobinopathies interfere with HbA1c?
they can give falsely low HbA1c as shorten the life span of RBC
conditions affecting globin chain synthesis are usually what pattern of inheritance?
autosomal recessive
what is thalassaemia?
decreased rate of globin chain synthesis
why are unbound globin chains dangerous?
they are toxic and result in haemolysis
inadequate Hb production in thalassaemia will lead to what kind of anaemia?
microcytic hypochromic anaemia
in alpha thaassaemia how many genes are lost in
1) alpha 0
2) alpha +
1) 2/4 genes lost
2) 1/4 genes lost
what is the severe form of alpha thalassaemia called?
HbH disease- 1 gene per cell
how is HbH formed in HbH disease?
excess B chains form tetramers called HbH which can’t carry oxygen
what symtpoms are seen in HbH disease?
jaundice due to haemolysis
inefective erythropoiesis
splenomegaly
what is the severst form of alpha thalassaemia?
Hb Barts hydrops fetalis syndrome
how many alpha genes are inherited in Hb Barts?
no alpha genes inherited from either parent- cannot make HbA
what kind of Hb is made in Hb Barts?
HbF- four gamma chains, extremely high affintiy fro oxygen to hardly any delivery to tissues
what kind of mutation usually causes disorder of beta chain synthesis in beta thalassaemia?
point mutation
does beta thalassaemia affect HbA and HbF?
no- only afects adult haemoglobin not foetal
how is beta thalassaemia intermedia treated?
occasional transfusion
(moderate severity)
when does beta thalassaemia major present?
6-24 months (as HbF falls)
what is the management of beta thalassaemia major?
regular transfusion to maintain Hb
what is the main concern with regular transfusions in beta thalassaemia major?
iron overload
if you suspect a thalassaemia what else should you check first to rule out anaemia?
ferritin
what are chelating drugs?
bind to iron formign complexes that can then be excreted in urien or stool
what is an example of a chelating drug used in iron overload?
desferrioxamine
