Down's Syndrome

This post has been a while coming but I wanted to research it properly as genetics is something that I am very interested in. Researching this has made me think of another possible career of research, if I get into Medical school.

Down’s syndrome

Down’s syndrome, named after the British physician who described it in 1866. It affects around 1/1000 babies in the UK (Down’s syndrome association website 18/3/12) and is more common in older women. It is also known as trisomy 21, referring to the extra chromosome which causes this disability. The baby is born with either an extra whole, or part of, chromosome 21. This occurs by chance at conception, and can be caused by faulty meiosis of the women’s eggs, where, in the final stages of meiosis one gamete has 3 chromosome 21s and the other only has one, or in familial Down’s syndrome, where part of chromosome 21 fuses to part of chromosome 14. The remaining genetic material is often lost in mitosis. This is called Robertsonian translocation. It is possible to carry this gene and be unaffected by Down’s as this only affects one gene from the homologous pair in carriers, and the “regular” gene can function as well by itself. 

Monosomy 21 (only one chromosome 21) seems much rarer, and often results in the infant dying fairly soon after birth. There are other trisomies which aren’t as common and can include trisomy 18 (Edward syndrome), 13 (Patau syndrome), or 8.

 It is possible to have partial or mosaic Down’s syndrome, or complete Down’s syndrome. Complete Down’s syndrome is as a result of a fault in meiosis, as stated above. Mosaic Down’s syndrome occurs when the foetus is developing. One of the cells divides but does so incorrectly, leaving one of the sister cells with an extra chromosome. This goes on to affect only part of the body, as opposed to complete Down’s where every cell has an extra chromosome. The third sub-type of Down’s is translocated or familial Down’s.

People with Down’s syndrome are usually easily recognised due to the prominent physical differences. Physical symptoms of Down’s include:

• eyes that slant upwards
• small ears
• flat back of head
• small mouth
• protruding tongue
• flattened nose bridge
• white spots on the iris (the coloured part of the eye), known as Brushfield spots
• short fingers
• broad hands with a single crease across the palm
• loose skin on the back of the neck
• loose joints (babies in particular may seem ‘floppy’)
• poor muscle tone (hypotonia)
• low birth weight
• vertical skin folds (epicanthic folds) between the upper eyelids and inner corner of the eye

Other symptoms include learning difficulties (memory problems, both short and long term, low attention spans, difficulty problem solving and difficulty understanding the consequences of their actions), and delayed development with “milestones” like learning to:

• Read
• Walk
• Speak
• And social skills

 There is no “cure” for Down’s (it is a disability, not a disease), but it is possible for the child to undergo treatment to help it with learning difficulties and other developmental problems, such as speech therapy. 

However, there are more severe complications which can occur as a result of Down’s. These include heart defects, 30% of which will be serious enough to need immediate attention after birth (NHS website 18/3/12), problems with hearing and vision, which affect around 50% of people born with Down’s, oral and thyroidal problems. Oral problems arise where the individual struggles to brush their teeth effectively or when they produce a lower level of saliva, allowing bacteria to damage gums and teeth. I found this particularly interesting as I didn’t even know that saliva helped with that. Thyroidal problems are when the person affected has hypothyroidism, where their thyroid doesn’t produce enough hormones. Your thyroid is responsible for your metabolism, or the rate at which chemical reactions take place in the body and as result can lead to weight gain, slow mental or physical reactions and dry or flaky skin, among others. It is possible for a person with Down’s to have hyperthyroidism, where the thyroid is overactive, but this is rarer. 

In conclusion, if intervention happens young, and the individual is offered sufficient support, both medically and educationally, there is very little reason for them not to be independent in at least some spheres of their adult life. I very much enjoy playing with the children at Mencap who have Down’s, and found them all fun loving and playful.

http://www.downs-syndrome.org.uk/about-us/key-facts-and-faqs.html

http://www.dummies.com/how-to/content/genetics-understanding-chromosome-disorders.html

http://www.nhs.uk/conditions/downs-syndrome/pages/introduction.aspx