LESSON 1: PART 1 - DOWN SYNDROME, MENTAL RETARDATION AND AUTISM

• G trisomy

• Mongolism

• trisomy 21

DOWN SYNDROME Aka

DOWN SYNDROME

A condition where chromosome 21 has a full or partial extra copy in some, or all, of that individual’s cells, thus called trisomy 21.

DOWN SYNDROME

results from faulty cell division affecting the 21st pair of chromosomes

DOWN SYNDROME

•the most common chromosome abnormality in humans and is accompanied by several disorders of the musculoskeletal system.

John Langdon Down

DOWN SYNDROME First studied by?

Jérôme Lejeune

identified Down syndrome as a chromosomal condition

• NONDISJUNCTION

• MOSAICISM

• TRANSLOCATION

TYPES OF DOWN SYNDROME

NONDISJUNCTION

most common type about 95%

NONDISJUNCTION

With this type, it is caused by an error in cell division

NONDISJUNCTION

where each cell in the body has 3 separate copies of chromosome 21 instead of the usual 2 copies

MOSAICISM

least type OF DOWN SYNDROME

MOSAICISM

affects about 1-2% of the people with Down syndrome.

MOSAICISM

when there is a mixture of two types of cells, where some containing the usual 46 chromosomes and some containing 47 (an extra chromosome 21)

TRANSLOCATION

accounts for a small percentage of people with Down syndrome (about 3%).

TRANSLOCATION

occurs when an extra part or a whole extra chromosome 21 is present, but it is attached to a different chromosome rather than being a separate chromosome 21, usually at chromosome 14

1:350

A 35 year old woman has about a————— chance of conceiving a child with Down syndrome

1:100

A 40 year old woman has about a————— chance of conceiving a child with Down syndrome

1:30

A 45 year old woman has about a————— chance of conceiving a child with Down syndrome

Increase maternal age

the only factor that has been linked to an increased chance of having a baby with Down syndrome resulting from nondisjunction or mosaicism

5%

ETIOLOGY DOWN SYNDROME: Approx. —- of the cases have been traced to the father

• 1:100

• age 40

ETIOLOGY DOWN SYNDROME: Once a woman has given birth to a baby with trisomy 21 (nondisjunction) or translocation, it is estimated that her chances of having another baby with trisomy 21 is ——- up until age ___.

• 3%

• 10-15%

ETIOLOGY DOWN SYNDROME: risk of recurrence of translocation is about — if the father is the carrier and ——— if the mother is the carrier.

35–50 %

ETIOLOGY DOWN SYNDROME: if one partner has Down syndrome, there is a ———- chance that their children will acquire the condition

• 76%

• 66%

NEUROPATHOLOGY DOWN SYNDROME: Overall brain weight in individuals with DS is ——- of normal, with the combined weight of the cerebellum & brainstem being even smaller: —- of normal

• Microcephaly

• microbrachycephaly

NEUROPATHOLOGY DOWN SYNDROME: ————— or ———————- with decrease secondary convolutions of the brain

• dendritic spines

NEUROPATHOLOGY DOWN SYNDROME: structural abnormalities in the —————- in the pyramidal tracts of the motor cortex

DOWN SYNDROME

structural abnormalities in the dendritic spines in the pyramidal tracts of the motor cortex

DOWN SYNDROME

usually have cognitive development profiles that suggest mild to moderate intellectual disability

DOWN SYNDROME

developmental milestones a little later than their peers.

DOWN SYNDROME

may also be problems with attention, a tendency to make poor judgments, and impulsive behavior.