Down Syndrome


What is Down Syndrome ? 

The term Trisomie 21 (French for Down Syndome), suggested by Jérôme Lejeune in the 1960’s and then validated by an international group of scientists, designs the whole of the physical and biological manifestations caused by the presence of a third chromosome 21, instead of 2.

It should definitively replace the term Down Syndrome (Syndrome de Down in French) and mongolism, as its use rests on a triple mistake.

  • Historical, because it was not Langdon Down who first described this syndrome, but the Frenchman Seguin and before him Esquirol with his ”furfuraceous diathesis” (first clinical description of Down Syndrome in 1833).

    Scientific, because this disease is not the consequence of “racial segregation” or of an archaic form of man, as supposed by Langdon Down, but of the presence of a supernumerary chromosome.


  • Ethical, because Langdon Down presupposed that the white race was the superior race and he described, as well as the Mongolian regression, an Ethiopian regression and a Malaysian regression.

A human being normally has 46 chromosomes. The chromosomes, derivate structures of the cell nucleus, contain the whole of the hereditary characters unique in each individual and are constituted essentially of deoxyribonucleic acid (better known as DNA) and proteins. These chromosomes are spread out organized as following:

  • 44 chromosomes organised in 22 pairs of chromosomes common to both sexes, also called autosomes.  These pairs are numbered from 1 to 22 and have the particularity of not carrying any genes that determine the sex (the smallest unity of genetic information is called gene). These pairs of chromosomes are classified in size, from the biggest to the smallest. The chromosome 21 therefore belongs to the 21st pair.
  •  2 sexual chromosomes which determine the sex: XX in women and XY in men.

In Down Syndrome, there are three copies of the chromosome 21 instead of 2, which causes there to be an excessive amount of the genes that are carried by this chromosome (about 300) an therefore an unbalance in the functioning of the organism.

Is Down Syndrome a disease ? 

A disease is an alteration of health, of the functions of living beings.

Down Syndrome is therefore a disease because of the presence of a supernumerary chromosome 21 which triggers organic and functional alterations whose association and evolution are characteristic of it.

On the other hand, the word disease implies the possibility of a medical intervention and treatment, which gives out a positive vision of Down Syndrome. This is why Jérôme Lejeune invented the term intelligence disease in order to complete those which already existed, i.e., intellectual deficiency or mental disability which presupposes the absence of the possibility of treatment.

The term disability is used in an economic and social perspective but certainly not in a medical one: a person with a disability is entitled to financial and social compensations which aim at re-establishing some sort of equality of chances. But there is no compensation whatsoever that could ever replace the fact of losing one’s liberty of disposing of the full use of one’s intelligence.

Is Down Syndrome a congenital disease ? 

A congenital anomaly is an anomaly which is present at birth whatever its cause may be (hereditary, viral, toxic…)

Down Syndrome is a constitutional affection as it is associated with a particular constitution, in this case the presence of three chromosomes 21.

This constitutional affection can be association with:

  • congenital anomalies, with or without malformations: heart diseases, digestive malformations, congenital cataract…
  • medical problems which occur during life : thyroid, epilepsy, Keratoconus…

A mental disability which remains constant

All these manifestations related to Down Syndrome are not present at birth but can occur later on. This is what justifies the patients’ regular check up by doctors who know which anomalies to look for at a given age.



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