Pnedintnc and Perinatal Epidemiology 1987, 1, 197-198

Correspondence

Sir

Competing Causes of Death in Young Cases of Myeloid Leukaemia

Recent work has shown that when leukaemias have fetal origins, levels of immunological competence are apt to fall to dangerously low levels during the latent phase of the disease [1,2]. Therefore, it is hardly surprising that the discovery of antibiotics was followed by a worldwide increase in the number of recognised cases. However, the available evidence suggests that early loss of immunological competence is even more typical of myeloid than lymphatic leukaemia, and the risk of infection deaths is certainly greater for infants than older children. Therefore it remains a mystery why the postwar increase in childhood leukaemias was all but confined to lymphatic cases and children over two years of age [3]. It is possible that the children who would have had myeloid leukaemia are still dying prior to clinical evidence of the condition. They could be stillbirths or sudden infant deaths (SIDS).

There already exists a rare type of myeloid leukaemia which affects infants and exhibits abnormally high proportions of fetal haemoglobin and other signs of fetal type erythropoesis [4]. Therefore there is no need to invent a type of leukaemia which might have anoxia as one of several competing causes of death. Furthermore, a recent study of 85 SIDS and 15 infants who had died from acute respiratory infections found exceptionally high proportions of fetal haemoglobin in both groups [5]. Finally, a common time for stillbirth of otherwise normal fetuses is during the second stage of labour (when there is most danger of dying from anoxia) and leukaemia deaths during peak incidence of SIDS (1-5 months) are not only extremely rare but hardly ever follow births in calendar months which (as seasons of birth) have associations with SIDS (i.e. births in the second half of each year) [6] .

The following attempt to resolve this problem would require an epidemiolo- gist (working in close association with a haematologist) to arrange for collection of blood samples from two groups of young infants: a control group consisting of healthy infants between 0 to 5 months of age, and a case group consisting of unexplained stillbirths, SIDS, and infants suffering from leukaemia or infections which are not responding to antibiotics.

The purpose of the blood tests would be to discover whether they provided any support for the following hypotheses: first, that the reason for the small

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198 Correspondence proportion of myeloid cases among childhood leukaemia is because, in these cases, there is faulty maturation of erythropoesis and myelocytes and consequent difficulty in coping with a rarified atmosphere as well as infections. The second hypothesis is that some evidence of these changes might be found in the blood of fetuses or infants who had died either from anoxia or from infections during the latent phase of myeloid leukaemia. Therefore the blood tests should be directed towards measuring proportions of fetal and adult haemoglobin and looking for other signs of faulty erythropoesis and leucopoesis.

Alice Stewart Department of Social Medicine University of Birmingham, UK

References

1 Kneale, G.W., Stewart, A.M. Pre-cancers and liability to other diseases. Br. 1. Cancer

2 Stewart, A.M., Kneale, G.W. The immune system and cancers of foetal origin. Cancer Imrnunol. Inmunother. 1982; 14110-116. 3 Hewitt, D. Some Features of Leukaemia Mortality. Br. I. Preu. SOC. Med. 1955; 981-88. 4 Weatherall, D.J., Edwards, J.A., Donohue, W.T.A. Haemoglobin and red cell enzyme changes in juvenile myeloid leukaemia. Br. Med. J . 1968; i:679-681. 5 Zielke, H.R., Krause, B.L. Activity of 5 enzymes of foetal haemoglobin in RBCs of infants dying from the sudden infant death syndrome (SIDS). Fed. Proc. 1982; 41(2):1148. 6 Stewart, A.M. Infant leukaemias and cot deaths. Br. Med. 1. 1975; ik605-607.

1978; 32448-457.