Down syndrome is the most common chromosomal disorder (chromosomes are structures contained in the cell nucleus) and is characterized by a surplus of 21 chromosome. In human somatic cells there are 46 chromosomes that are grouped in 23 pairs.
Condition occurs with predilection in males, the risk increases with maternal age.
From clinical point of view, this condition is characterized by a dismorphic syndrome (change of the normal appearance) which involves:
- changes of the face – microcephaly (skull size is below the size of appropriate age), flat neck, round facies, short neck, hypertelorism (increased distance between eyeballs), epicantus, palpebral fissure is oblique upward and outward, Brushfield spots (circular depigmented areas of the iris), small nose with broad-based, half-open mouth with tongue in protrusion (pushed forward), small round ears implanted lower;
- changes of limbs – short and broad hands, clinodactylitis (bone deformation which consists in lateral tilting of the extremities of fingers) of the five finger, plantar flattened hollow, wide gap between first finger of the foot and finger 2 from foot;
- dry skin;
- mental retardation is less evident at birth, children are affectionate, difficulties in speech, like the game, arrange items in order;
- short stature, obesity.
Down syndrome may be associated with several malformations of organs and systems:
– Congenital heart malformations – atrioventricular canal, ventricular septal defect, persistent ductus arteriosus;
– Ocular abnormalities – cataract, astigmatism, strabismus, congenital glaucoma;
– Digestive malformations – duodenal stenosis, anal imperforation;
– Hematology – these people have an increased risk of developing various forms of leukemia;
– Immunology – immune system is weak, favoring the development of infections;
– Metabolic – changes in blood glucose;
– Sterility in males, females are fertile.
Down syndrome is a condition that can be detected before birth by cytogenetic analysis of amniotic fluid or chorionic villus. This analysis is carried out if there are changes in ultrasound or in triple test (alpha feto protein dosage, beta-hCG, unconjugated estriol) or if the mother is older.