Down Syndrome

Sayed Zeeshan AlviPremed 3

What is it?

Down syndrome, also known as Trisomy 21, is a genetic disorder that presents complications in a persons physical and mental capabilities.

History

During ancient times, infants with disabilities were either abandoned or killed.

Doctor John Langdon Down was the first to describe the characteristics of Down syndrome in a published report in 1866.

By the 20th century, Down syndrome was formally recognized as a mental disability.

Causes

Genetics

Trisomy 21

Translocation

Trisomy 21

AKA 47,XX,+21 for females and 47,XY,+21 for males

caused by a failure of the 21st chromosome to separate during gamete formation.

Results in having an extra chromosome present in either egg or sperm(24 chromosomes).

Final zygote has 47 chromosomes, 3 being chromosome 21, thus Trisomy 21

88% of cases of trisomy 21 result from non separation of the chromosomes in the mother, 8% from non-separation in the father, and 3% after the egg and sperm have merged

In mosaic Down syndrome 1 to 2.5% of cases, some of the cells in the body are normal and others have trisomy 21

Translocation

Extra chromosome 21 occurs due to a Robertsonian translocation (2–4% chance).

The long arm of chromosome 21 is attached to another chromosome, often chromosome 14.

Can occur as a new mutation or hereditary

Signs

Complications

Heart: congenital heart disease in newborns with Down syndrome is around 40%.

Hearing and Vision:Vision problems occur in 38 to 80%. Between 20 and 50% have strabismus, in which the two eyes do not move together. Cataracts occur in 15%, and may be present at birth.

Neurological: Individuals with Down syndrome have mild (IQ: 50–70) or moderate (IQ: 35–50) intellectual disability with some cases having severe (IQ: 20–35) difficulties.

Fertility: Males with Down syndrome usually do not father children, females have lower rates of fertility relative those who are unaffected. Fertility is estimated to be present in 30–50% of women.

Epidemiology

Down syndrome occurs in about 1 per 1000 births and results in about 17,000 deaths.

Maternal age affects the chances of having a pregnancy with Down syndrome. At age 20 the chance is 1 in 1441; at age 30 it is 1 in 959; at age 40 it is 1 in 84; and at age 50 it is 1 in 44

Management

Screen for Diseases

Hearing Aid

Speech Therapy

Sign Language

Monitor heart (electrocardiogram and ultrasound of the heart)

Physical Therapy

Tonsillectomy(prevent sleep apnea)

Sources

http://en.wikipedia.org/wiki/Down_syndrome

http://www.ndss.org/

http://www.gizmodo.com.au/2013/07/scientists-may-have-found-a-genomic-off-switch-for-downs-syndrome/

http://www.larasig.com/sites/larasig.com/files/images/trisomy21_0.jpg

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