L2: Down Syndrome Flashcards
Epidemeology of Down Syndrome
Def & Results of Meiosis
Cytogenic Types of Down Syndrome
- Complete Trisomy 21
- Mosaic Down Syndrome
- Translocation Down Syndrome
What Characterizes Complete Trisomy 21?
The Most Common
Complete Trisomy 21
- Karyotyping
47,XX + 21
Incidence of Complete Trisomy 21
What Is Complete Trisomy 21 dependent on?
Maternal Age
Cause of Complete Trisomy 21
- Non-disjunction of chromosome 21 during meiotic division (80 % in maternal meiosis I)
- lt occurs during oogenesis more than spermatogenesis.
Risk of Recurrence in Complete Trisomy 21
1-2% regardless of maternal age
What Characterizes Mosaic Down Syndrome?
The Best Type
Mosaic Down Syndrome
- Karyotyping
47, XX + 21 / 46, XX
Incidence of Mosaic Down Syndrome
1-2% of cases (more with maternal age)
Cause of Mosaic Down Syndrome
- Non-disiunction occurring early in the division of the zygote, which results in two lines of cells (normal & trisomic)
Risk of Recurrence i Mosaic Down Syndrome
Same as Complete
Clinical manifestations in mosaic type are โฆ.. than complete trisomy
Iess
- ln mosaic type, non-disjunction occurs during โฆ. division
- while in complete type, it occurs during โฆ. division
- mitotic
- Meiotic
What Characterizes Translocation Down Syndrome?
The Most Serious Type
Translocation Down Syndrome
- Karyotyping
46,XX, t(14q, 21q)
Incidence of Translocation Down Syndrome
o lncidence 3- 4%
o Common in young age < 25 years
o Robertsonian translocation is the most common type
โฆโฆ. translocation is the most common type
Robertsonian
Cause of Translocation Down Syndrome
Risk of Recurrence in Translocation Down Syndrome
Types of inherited Translocation
- D/21 Translocation
- G/21 Translocation
D/21 Translocation
- lf ovum contains translocation chromosome only, fertilization by normal sperm will Iead to โฆ..
BTC โ> (45 chromosome but genome of 46 chromosomes)
- lf ovum contains translocation chromosome and normal chromosome 21, fertilization by normal sperm will lead to โฆ..
Down syndrome (46 chromosome but genome of 47 chromosomes)
G/21 Translocation
Pathogenesis of Down Syndrome
CP of Down Syndrome
A LOTTTTTTT
Down Syndrome
- Constant Features
- Delayed physical growth
- Delayed mental development (mild to moderate mentaI retardation)
- Hypotonia
CP of Down Syndrome
- Head
CP of Down Syndrome
- Eyes
CP of Down Syndrome
- Nose
Small with depressed nasal bridge
CP of Down Syndrome
- Ears
- Small
- Low set & backward displacement
CP of Down Syndrome
- Neck
Short & Webbed
CP of Down Syndrome
- Tongue
- Protruded (small oral cavity)
- Fissured (scrotal)
CP of Down Syndrome
- Ribs
Unilateral or bilateral absence of one rib
CP of Down Syndrome
- Hands
Def of Brachydactyly
Short + stocky
Def of Clinodactyly
lncurved little fingers
- Due to rudimentary or absent mid phalanx of
little finger)ใ
Def of Simian Crease
Transverse palmer crease (partial or complete)
CP of Down Syndrome
- Feet
CP of Down Syndrome
- GIT & Abdomen
CP of Down Syndrome
- CoHD
CP of Down Syndrome
- Endocrine
CP of Down Syndrome
- Genitalia
Poorly developed
CP of Down Syndrome
- Immunity
Impaired cellular & humeral immunity
Complications of Down Syndrome
Most Common Causes of Death Down Syndrome
- Accidents due to mental retardation
- Sudden death due to arrhythmia
Most Common Presentation of complication Down Syndrome
- Heart failure due to congenital heart disease
- Recurrent chest infections due to CHD, i immunity, most common presentation Hypotonia, aspiration & Decreased immunity (Predominantly T cell dysfunction, however, both T & B cells functions are affected)
INVx for Down Syndrome
- Prenatal
- After Birth
INVx for Down Syndrome
- Prenatal Dx
INVx for Down Syndrome
- Prenatal Dx (1st Trimester)
INVx for Down Syndrome
- Prenatal Dx (2nd Trimester)
Maternal Serum Screening in 2nd Trimester for Down Syndrome
INVx for Down Syndrome
- After Birth
DDx of Down Syndrome
Managment Plan for Down Syndrome
Genetic Counseling for Down Syndrome
Risk of Recurrencre in Down Syndrome
