A STUDY OF THE SURVIVAL RATE OF CASES OF SICKLE-CELL ANAEMIA
A STUDY OF THE SURVIVAL RATE OF CASES OF SICKLE-CELL ANAEMIA
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DOI：
10.1136/bmj.1.5021.738
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发表时间：
1957-01-01
影响因子：
--
通讯作者：
JACOB, GF
中科院分区：
文献类型：
--
作者：
JACOB, GF
It is now generally accepted that the phenomenon of the sickling of red cells at reduced oxygen tensions is due to the presence of greater or lesser amounts of an abnormal haemoglobin within the cells. The production of this haemoglobin is controlled by a gene which is allelic to the gene controlling normal haemoglobin production. The heterozygous inheritance of this sickle-cell gene produces the harmless sickle-cell trait, while the homozygote is manifest as sickle-cell anaemia. This anaemia is characterized by haemolysis with intermittent crises and is usually fatal in childhood. This death in child-hood of the homozygotes must remove abnormal genes from the population, and the immediate question arises of how, in the face of this recurrent gene loss, the gene frequency can be maintained at the high levels at which it is found in many African tribes. The answer seems to lie in the interaction of three main factors. Firstly, recurrent mutations must play some part, though it is highly improbable that they could provide the sole replacement of all the genes lost by childhood deaths. Secondly, it is now well established that the heterozygote sickler enjoys some advantage over the normal in respect of falciparum malaria, though the magnitude and exact mechanism of this effect are not yet clear. Thirdly, there is the fact that while most subjects with sickle-cell anaemia die in childhood, some few do survive to adult life and contribute abnormal genes to the next generation. This paper presents some evidence on this third factor as found in a single African tribe in Uganda.The older literature on the natural history of sickle-cell anaemia has becomelargely invalidated by the recent discovery of other genetically controlled abnormal haemoglobins and by the description of microdrepano-cytic disease. Both this latter disease and the anaemia often resulting from the double inheritance of two abnormal haemoglobins may produce a clinical picture closely similar to sickle-cell anaemia. In East Africa, however, other abnormal haemoglobins have not been found among the African tribes (Jacob, 1955; Roberts and Lehmann, 1955) and thalassaemia has never been detected. The same situation appears to obtain in the Belgian Congo. A high degree of validity can therefore be attached both to clinical reports in children and to simple electrophoretic surveys in adults directed towards defining the survival rate of cases of sickle-cell anaemia in these two areas. Nevertheless, published work has produced somewhat variable estimates of survival rates. In Kenya, Allison (1954) examined 70 adult sicklers of the Luo tribe by paper electrophoresis and found two cases with the pattern of sickle-cell anaemia. He calculated that these two represented a 35% survival rate to adult life. He later suggested that the survival rate in Africa was more likely to be in the region of 200% on the basis of figures collected from the Musoma tribe of Tanganyika (Allison, 1956). In a survey of the Baamba tribe in Uganda, Lehmann and Raper (1956) found no case showing the electrophoretic pattern of sickle-cell anaemia in a randomsample of 478 adults. They conclude" that the survival of sickle-cell homo-zygotes plays no significant part in the maintenance of the high sickling rate in the Baamba." Workers in the Belgian Congo have expressed the same opinion on the basis of clinical observations in children. The Lambotte-Legrands (1955) state that the great majority of patients die in childhood, and Vandepitte (1955) estimates that only about 1% survive to adult life. It was therefore decided to undertake an electrophoretic survey of adults of the Baganda tribe in an attempt to obtain a more exact figure for …
