CHROMOSOME ABNORMALITIES AND THE 

 LEUKAEMIC PROCESS 



J. LEJEUNE 



Faculte de Medecine, Institut de Progenese, Paris, France 



I am taking the opportunity of adding a few words to what has already been 

 said about the role of chromosomal changes in the occurrence of leukaemia. 

 Very briefly it can be stated that we have three kinds of indication. 



A. Association of mongolism with leukaemia 



Even before mongolism was recognized as bemg determined by a trisomy, 

 the correlation between this congenital disease and acute leukaemia had been 

 described. 



The analysis of Stewart and Hewitt (1959) shows that mongols are 

 possibly twenty times more frequently leukaemic then normal children. 



The nature of this leukaemia of mongols is also very special for in 37 

 cases, Stewart (1961) reports 21 blast-cell, and 16 acute lymphoblastic cases. 

 The conclusion of Stewart being that these leukaemias are confined to one 

 type only: the stem-cell type. 



B. Association betiveen chronic myeloid leukaemia and 'partial deletion of a small 



acrocentric 



The discovery of NoweU and Hungerford (1960) that there were two 

 populations of cells, one entirely normal, the other containing cells exhibiting 

 a very small, acrocentric, chromosome has been repeatedly confirmed for 

 chronic myeloid leukaemia. 



The pubUshed data are summarized in Table I. 



Hence in 28 cases the smaU chromosome, called Ph^ was observed. This 

 can hardly be considered as a pure coincidence. 



The nature of the Ph^ is not definitely established but it is most likely 

 that it is a normal small acrocentric (21 or 22) which has lost more than half 

 of its long arms. 



C. Association between acute myelohlastic leukaemia and deletion of a small 



acrocentric 



To my personal knowledge 4 cases have now been reported. One by 

 Hungerford (1961) with 6 cells with 45 chromosomes (without determination 

 of the lost one) among 61 examined; 1 by Fortune et al. (1962) exhibiting a 



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