Page 118 - Essential Haematology

104 / Chapter 7 Genetic disorders of haemoglobin

(a) (b)

Figure 7.19 (a) Sickle cell anaemia: peripheral blood fi lms showing deeply staining sickle cells, target cells and
polychromasia. (b) Homozygous Hb C disease: peripheral blood fi lm showing many target cells, deeply staining
rhomboidal and spherocytic cells.

some children or adults who are having three or Combination of h aemoglobin S with
more painful crises each year. It should not be o ther g enetic d efects of h aemoglobin
used during pregnancy.

9 Stem cell transplantation can cure the disease The most common of these are Hb S/ β - thalassaemia,
and many patients have now been successfully and sickle cell/C disease. In Hb S/ β - thalassaemia,
treated. The mortality rate is less than 10%. the MCV and MCH are lower than in homozygous

Transplantation is only indicated in the severest Hb SS. The clinical picture is of sickle cell anaemia;
of cases whose quality of life or life expectancy splenomegaly is usual. Patients with Hb SC disease
are substantially impaired. have a particular tendency to thrombosis and pul-
10 Research into other drugs (e.g. butyrates) to monary embolism, especially in pregnancy. In
enhance Hb F synthesis or to increase the solu- general, when compared with Hb SS disease, they
bility of Hb S is taking place. have a higher incidence of retinal abnormalities,
milder anaemia, splenomegaly and generally a
longer life expectancy. Diagnosis is made by haemo-
globin electrophoresis, particularly with family
Sickle c ell t rait studies.

This is a benign condition with no anaemia and
normal appearance of red cells in a blood fi lm. Haemoglobin C d isease
Haematuria is the most common symptom and is
thought to be caused by minor infarcts of the renal This genetic defect of haemoglobin is frequent in

papillae. Hb S varies from 25 to 45% of the total West Africa and is caused by substitution of lysine
haemoglobin (Fig. 7.12 ). Care must be taken with for glutamic acid in the β - globin chain at the same

anaesthesia, pregnancy and at high altitudes. point as the substitution in Hb S. Hb C tends to