Haematological disorders associated with Thalassaemia

Normally α and β in 1:1 ratio.
Precipitation of globin chains within RBC precursors, which causes ineffective erythropoiesis.
The precipitation of globin chains in mature RBC leads to haemolysis.

β Thalassaemia

Excess of α, precipitate in erythroblasts and RBC’s causing ineffective erythrocytosis and haemolysis.

Type of thalassaemia Haematological problems

Minor (trait) Usually symptomless microcytosis but mild anaemia may be present

Intermedia Moderate anaemia, may have splenomegaly, bone deformities.

Major (Cooley’s anaemia) Severe anaemia, extramedullary haemopoeisis which leads to hepatosplenomegaly and bone expansion giving the “hair on end” of bone appearance.


α Thalassaemia
Excess of β, but as all normal haemoglobin contains α globin, if all 4 genes are deleted, the haemoglobin barts produced are incapable of carrying oxygen and the foetus dies.

Type of mutation Haematological problems
4 gene Fatal- pale, oedematous, hydrops fetalis
3 gene Moderate anaemia, splenomegaly
2 gene Microcytosis with or without mild anaemia
1 gene Usually normal blood



Precipitation: globin chains separated out from solution into a solid form.
Precursors: The reactions that form red blood cells (RBC).
Erythropoiesis: The production of erythrocytes (RBC).
Haemolysis: The rupturing of RBC’s.
Hydrops fetalis: enormous liver and spleen
(Hepato)splenomegaly: enlarged spleen (and liver)
Microcytosis: the presence of microcytes (abnormally small red blood cells) in the blood
Oedematous: An excessive accumulation of serous (serum) fluid in tissue spaces or a body cavity
Extramedullary haemopoiesis: The formation and development of blood cells outside the bone marrow, as in the spleen; liver; or lymph nodes.
Erythroblasts: nucleated (with nucleuses) cells that develop into RBC’s.
Erythrocytosis: excess of RBC’s