Down syndrome (DS) is a genetic disorder caused by the presence of an extra copy of the chromosome 21 instead of the two usual (Trisomy of pair 21).
People with this disorder are characterized by having a variable degree of intellectual disability and specific appearance features which give them a recognizable look, furthermore they have a higher probability than the general population to suffer some pathologies, especially in the heart, digestive and endocrine system.
This is caused by the excess of synthesized proteins by the extra chromosome.
Down syndrome – Trisomy 21
The cells in human beings have each one in its nucleus 23 pairs of chromosomes. Each progenitor provides their descendants with half of the genetics information, in the form of a chromosome of each pair. 22 of these pairs are called autosomes and the last one corresponds to the sexual chromosomes (X or Y).
Traditionally the pairs of chromosomes are described and named according to its size, from pair 1 to 22 (from large to small) plus the pair of sexual chromosomes previously mentioned. The chromosome 21 is actually the smallest one, so that it should occupy the place 22, but because of a mistake in the Convention of Denver in 1960, in which the Down syndrome was assigned the pair 21, and still exists nowadays, it was then for practical reasons left to this nomenclature.
The chromosome 21 contains approximately 1% of the genetics information of an individual in more than 400 genes, although nowadays it is only known accurately the function of a few of them.
Not all the causes which originate the erroneous disjunction are fully known. Like in other similar processes, some hypotheses with multiple factors have been proposed (environmental exposure, cellular aging…) without any achievement to establish a direct relation between any of the causing agents and the emerging of the trisomy.
The only element which presents a stable association by statistics with the syndrome is the maternal age, what seems to support the theories which emphasize the deterioration of the genetic material over time.
After the free trisomy the most frequent cause of the onset of excess in the genetic material is the translocation. In this variant the extra chromosome 21 (or an extract of it) is found “attached” to another chromosome (frequently to one of the two chromosomes of pair 14) giving the genetic count a total of 46 chromosomes in each cell. In this case there is not a problem with the chromosome disjunction, but one of them carries an “extra” fragment with the genes of the “translocated” chromosome.
The frequency of this gene variant is approximately in 3% of all the DS.
The less frequent form of trisomy 21 is the so-called “mosaic” (round 2% of the cases). This mutation occurs after the conception, so the trisomy is no present in each of the cells of the individual with DS, but only in the ones whose stock originates in the mutated cell. The percentage of affected cells can range from a few to almost all of them, according to the moment in which the anomalous segregation of the equivalent chromosomes was produced.
A vision of future
According to the current data it can be assumed that the majority of people with Down syndrome have a light or moderate intellectual impairment, unlike the old descriptions in which it was asserted that the impairment was severe. This change is due to the specific programmes that are currently applied (like the early stimulation and all of the health programmes that improve the quality of life) like to the opening and enriching of the environment that, in conjunction and in a non-specific way, are affecting the children of the current population in general, included the ones who have Down syndrome.
It is encouraging to note that when a good educational action persists there is no indication of impairment or personal regression in the change of one life stage to the other (from baby to child and subsequently to teenager). That means that people with Down syndrome can continue to make progress and develop when offered the necessary and adequate support. Despite the fact that the rhythm of growth of their mental age is slower than the one of their chronological age, in any case this means that the development stops (provided the correct educational action remains).
There is a cluster of common characteristics:
- The learning capacity is much slower.
- It is necessary to teach them many of the things that other children without Down syndrome would learn by themselves.
- The process of learning needs to be implemented in stages, taking into account the own characteristic of the people with Down syndrome.
- And it is not advisable to adopt a passive attitude. The educator needs to compensate, encourage, activate and look for alternatives that improve the inherent difficulties.
In the face of the major progress achieved in the development and education of the people with Down syndrome during the last 25 years it is vital and more logical to emphasize and insist on the positive aspects and the real abilities that the child is able to develop through all his/her life, and not stress that much the problems which might arise. The care and treatment carried out have to attend the needs of the child and their family, considered in its totality. Children, youth and adults with Down syndrome might have some similar problems between them, but each one is an individual with personality and different and unique characteristics.
To obtain the optimum development of a person with Down syndrome it is required to act as individual and continuously with the following detailed action plan:
- Maintenance of good health.
- Personal training and development of their cognitive and adaptive abilities.
There is no current medical treatment able to “cure” Down syndrome, or able to eliminate the extra chromosome 21, or that removes the actions of the gene copies that exist in excess. Although there is good and many therapeutic strategies through which it is accomplished to integrate the person with Down syndrome to the society, where he/she will be able to develop his/her multiple skills and own abilities.