Chapter 7 in Haematology
(Genetic disorder of haemoglobin) summary
-Genetic disorders of haemoglobin fall into
two main groups:
1-The
thalassaemias in which synthesis of the alpha or beta globin chain is reduced.
2-Structural
disorders in which an abnormal haemoglobin is produced.
-The alpha or beta
thalassaemias occur clinically as minor forms with
microcytic hypochromic red cells and a raised red cell count with or without
anaemia.total absece of function of all four alpha globin genes causes hydrops
fetalis.
-Total absencce of function
of both beta globin genes causes beta thalassaemia
major , a transfusion –dependent anaemia associated with iron overload. Thalassaemia
intermedia is a clinical term for a group of disorder showing mild to moderate
anaemia and is usually caused by variants of beta thalassaemia.
-The most frequent structural
defect of haemoglobin is the sickle mutation in the beta globin
chain causing, in the homozygous form, a sever haemolytic anaemia, associated
with vaso-occlusive crises.these may be painful affecting bone or affect soft
tissue (e.g.chest,spleen or central nervous system).crises may also be
haemolytic or aplastic.
-Antenatal
diagnosis using PCR technology to amplify chorionic villous DNA is used to
detect sever genetic defect of haemoglobin production,with termination of the
pregnancy if appropriate .
From book:
Essentail Haematology A.V.HOFFBRAND,P.A.H.MOSS.6EDITION
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