Down syndrome

Down syndrome or trisomy-21 is a genetic disorder. The genetic material of chromosome 21 occurs in triplicate (instead of in duplicate).  

Children with Down syndrome have both mental and physical problems. The syndrome occurs in about 4.6 out of 10,000 births. 

Down syndrome is caused by an extra copy of chromosome 21. Normally, a human has 46 chromosomes in every cell of the body. Someone with Down syndrome has a total of 47 chromosomes. 

This leads to problems in the development of the body and brain. It is not known why Down syndrome occurs. The chances of having a baby with Down syndrome increase with the age of the mother. 

In 96% of people with Down syndrome, the cause is not hereditary. 

If Down syndrome is suspected, the following examinations can be performed: 

Prenatal tests: 

• Non-invasive screening test: used to detect trisomy 21 in the baby by measuring the baby’s DNA in the mother’s blood. 
• Chorionic villus sampling (CVS): a small biopsy of the placenta is taken for specific genetic testing. 
• Amniocentesis: a needle is inserted into the amniotic sac that surrounds the foetus.  
• Ultrasound: sound waves are used to create an image of the foetus’ internal organs.  

Diagnostic testing after birth: 

• FISH (fluorescence in situ hybridisation): rapid blood test to check for extra material from chromosome 21. 
• Karyotype test: blood test that provides further information on the type of Down syndrome. 

Some common physical features of Down syndrome include: 

• Flattened face 
• Short neck 
• Almond-shaped eyes  
• Small ears 
• Delay in development 
• Intellectual disability 
• Vision and hearing problems 
• A tongue that tends to stick out of the mouth 
• Small hands and feet 
• Shorter in height 
• Heart problems 
• Dental problems 
• Gastrointestinal problems 
• Neurological problems  
• Thyroid abnormalities: higher TSH level, thyroid hypoplasia (thyroid gland that is too small), higher risk of autoimmune thyroid inflammation 

There is no cure for Down syndrome. Treatment is focused on reducing the symptoms/characteristics of the syndrome.   

Treatment might include: 

• Medical treatment for heart problems 
• Physical, speech and behavioural therapies to support a child in his/her development 
• Educational therapy 
• Treatment with thyroid hormone in case of hypothyroidism (insufficient production of thyroid hormone)