Exam 3: Down Syndrome Flashcards
What is the average lifespan of a person with down syndrome?
60
In down syndrome, which chromosome has 3 copies instead of 2?
21 - Called Trisomy 21
T or F: Down syndrome is the most common chromosomal disorder?
True
What are the 3 types of transmission?
Nondisjunction (95% of cases)
Translocation (4% of cases)
Mosaicism (1-% of cases)
What happens in nondisjunction transmission?
In Trisomy 21, there is an error in cell division called “nondisjunction”. This results in a baby being born with an extra copy of chromosome 21, meaning there are three copies of chromosome 21 instead of the usual two. As the embryo develops, the extra chromosome is replicated in every cell of the body.
What happens in translocation transmission?
In translocation, part of chromosome 21 breaks off during cell division and attaches to another chromosome, typically chromosome 14. While the total number of chromosomes in the cells remain 46, the presence of an extra part of chromosome 21 causes the characteristics of Down syndrome.
What happens in mosaicism transmission?
Mosaicism occurs when nondisjunction of chromosome 21 takes place in one - but not all – of the initial cell divisions after fertilization. In these cases, there is a mixture of two types of cells - some containing the usual 46 chromosomes and others containing 47. Those cells with 47 chromosomes contain an extra chromosome 21.
Which types of down syndrome are inherited and which are not?
Nondisjunction (95%): NOT inherited
Translocation (4%): Inherited
Mosaicism (1%): NOT inherited
T or F: 80% of down syndrome babies are born to women over the age of 35?
False; 80% of down syndrome babies are born to women under the age of 35 because most child bearing women are younger. However, the chances of having a child with down syndrome increases with increased age.
What is a major risk factor for down syndrome in an infant?
A. Maternal age younger than 16
B. Maternal age older than 35
C. A positive family history of down syndrome
D. A positive family history of genetic disease
The risk factor of having an infant with down syndrome is greater when the mother is older than 35
What type of genetic screening/testing is available for down syndrome and when do we do it?
10-14 weeks:
- NIPTs (non-invasive prenatal testing) serum screening (looking for chromosomal issues and if + would do further testing to confirm)
- Ultrasound (at least 11 weeks) to determine thickness of nuchal fold
- Chorionic villus sampling (invasive)
15-22 weeks:
- Quad serum screen (checks for 4 different hormones and calculates the risk for trisomy 13, 18, and 21)
- Amniocentesis (invasive)
Down syndrome presenting characteristics
Usually diagnosed immediately following birth because of distinctive phenotype
More than 50 physical characteristics, none of which are diagnostic
Most common: generalized hypotonia (weak floppy muscles), round face that appears flat, epicanthal folds, transverse palmar creases (Simian crease), small low-set ears, small mouth with protruding tongue, small head, brushfield spots on eyes, short nose, small broad hands, ligament laxity/hip problems, etc.
What are some issues to monitor for through the patient’s life?
Congenital heart defects (50%) Congenital hearing loss Visual problems/cataracts Sleep apnea Early onset Alzheimer disease
What do we need to be concerned about for a sports physical and why?
Up to 17% of downs patients have atlantoaxial instability (increased distance between the C1 and C2 joints).
Medical clearance necessary for sports.
Order cervical spine X-rays (including lateral view).
Potential to cause spinal compression
Early signs and symptoms include head tilt, torticollis, or deterioration in gait.
Are there any restrictions for sports?
With atlantoaxial instability:
Restricted from playing contact sports (basketball, tackle football, soccer, etc) and other high risk activities (trampoline jumping).
Without atlantoaxial instability:
May participate in low impact sports and sports not requiring extreme balance
