This document discusses trisomy, which is a type of aneuploidy where there are three instances of a particular chromosome instead of the normal two. It describes how trisomy occurs due to errors in meiosis where chromosomes fail to separate properly. The most common types of trisomy in humans are trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome). Trisomy can cause birth defects, intellectual disabilities, and shortened life expectancy depending on which chromosome is involved. Rare cases of other trisomies like 8, 9, 14, 16, and 22 are also discussed.

2. Trisomy

3. Prepared by :
Dr.Maher Shoblak Dr. Zuhair Dajani
Dr. Mary Baraka

4. Trisomy
• A trisomy is a type of polysomy in which
there are three instances of a particular
chromosome, instead of the normal two.
A trisomy is a type of aneuploidy
(an abnormal number of chromosomes)

5. Trisomy
• Description and causes
• Most organisms that reproduce sexually have
pairs of chromosomes in each cell, with one
chromosome inherited from each parent. In
such organisms, a process called meiosis
creates cells called gametes (eggs or sperm)
that have only one set of chromosomes. The
number of chromosomes is different for
different species. Humans have 46
chromosomes (i.e. 23 pairs of chromosomes).
Human gametes have only 23 chromosomes.

6. Trisomy
• If the chromosome pairs fail to separate
properly during cell division, the egg or sperm
may end up with a second copy of one of the
chromosomes. (See non-disjunction) If such a
gamete results in fertilization and an embryo,
the resulting embryo may also have an entire
copy of the extra chromosome.

7. Trisomy
• The most common types of autosomal
trisomy that survive to birth in humans are:
• Trisomy 21 (Down syndrome)
• Trisomy 18 (Edwards syndrome)
• Trisomy 13 (Patau syndrome)
• Trisomy 9
• Trisomy 8 (Warkany syndrome 2)
• Trisomy 22

8. Trisomy
• Of these, Trisomy 21 and Trisomy 18 are the
most common. In rare cases, a fetus with
Trisomy 13 can survive, giving rise to Patau
syndrome. Autosomal trisomy can be associated
with birth defects, intellectual disability and
shortened life expectancy.
• Trisomy of sex chromosomes can also occur and
include:
• XXX (Triple X syndrome)
• XXY (Klinefelter syndrome)
• XYY

9. Trisomy
• Compared to trisomy of the autosomal
chromosomes, trisomy of the sex chromosomes
normally has less severe consequences.
Individuals may show few or no symptoms and
have a normal life expectancy

10. Chromosomes
• Chromosomes are made of
DNA.
• Each contains genes in a linear
order.
• Human body cells contain 46
chromosomes in 23 pairs –
one of each pair inherited
from each parent
• Chromosome pairs 1 – 22 are
called autosomes.
• The 23rd pair are called sex
chromosomes:
XX is female, XY is male.

11. Structure of chromosome

12. Identifying chromosomes
Chromosomes can be identified by:
• Their size
• Their shape (the position of the
centromere)
NB Chromosomes are flexible
• Banding patterns produced by specific
stains (Giemsa)
Chromosomes are analysed by organising
them into a KARYOTYPE

13. Genes in chromosomes

14. •Definitions
• Gene : segment of DNA Which controls
the production of a particular
polypeptide chain located in
chromosome .
• It is Greek word .. Genos means origin .

15. Mitosis: is ordinary cell division among the
cells of the body.
During mitosis the chromosomes are divided
evenly, so that each of the two daughter cells
ends up with 1 copy of each chromosome.
For humans: start with 46 dyad chromosomes in 1
cell, end with 46 monads in each of 2 cells.
Stages: prophase, metaphase, anaphase,
telophase.

17. Meiosis: is the special cell division that
converts diploid body cells into the haploid
gametes.
Only occurs in specialized cells.
Takes 2 cell divisions, M1 and M2, with no DNA
synthesis between.
In humans, start with 46 chromosomes (23
pairs) in dyad state.
After M1, there are 2 cells with 23 dyad
chromosomes each.
After M2 there are 4 cells with 23 monad
chromosomes each.

19. Non disjunction

23. Obtaining a Sample
Fetal samples for karyotypes are commonly
obtained in two ways
1.Amniocentesis – sample taken from the
fluid of the amniotic sac
2.Chorionic Villus Sampling – sample taken
from the fetal tissue that forms part of the
placenta

24. Trisomy 13 (Patau Syndrome)
• 1st described by Bartholin (1657) & redefined by
Patau (1960).
• Chromosomal complement: 47,XX,+13 (female)
or 47,XY,+13 (male)
• Phenotype: Male or female
• Incidence: 1:12,000 (increases with the age of
mother)

25. Features of Patau Syndrome
• Mental deficiency
• Low birth weight
• Abnormal development
of frontal lobe
• Absence of corpus
callosum
• Hypoplasia of cerebellum
• Sloping forehead
• Scalp defects
• Malformed ears
• Congenital heart defects
• Renal tract anomalies
• Microphthalmia
• Bilateral cleft lip/palate
• Polydactyly with
rudimentary digits
• Rocker-bottom heel

26. Patau syndrome

27. Patau syndrome

28. Trisomy 18 (Edward Syndrome)
• 1st described by Johin Edward (1960)
• Chromosomal complement: 47,XX,+18
(female) or 47,XY,+18 (male)
• Phenotype: Male or female
• Incidence: 1:8000

29. Features of Edward Syndrome
• Mental deficiency
• Growth retardation
• Prominent occiput
with elongated head
• Webbing of the neck
• Short sternum
• Micrognathia
• Low-set malformed
ears
• Ventricular septal
defects
• Renal anomalies
• Clenched fists with
overlapping of fingers
• Hypoplastic nails

30. Edward syndrome

31. Trisomy 21 (Down Syndrome)
• 1st described by Johen Down (1866)
• Chromosomal complement: 47,XX,+21 (female) or
47,XY,+21 (male)
• Phenotype: Male or female
• Incidence: 1:800 (increases with the age of
mother)

32. • |
Features of Down Syndrome
• Short height
• Severe mental
deficiency with decline
in the IQ with age
• Brachycephaly with flat
face and occiput
• Flat and low nasal
bridge
• Upward slant to
palpebral fissures
• Malformed large ears
• Epicanthal folds of the
eyes
• Brushfield spots in iris
• Renal anomalies
• Prominent and
protruding tongue
(scrotal tongue)
• Simian crease
• Clinodactyly of 5th digit

33. Down Syndrome

34. • |
Down syndrome

35. Down syndrome

36. Down syndrome

38. 1. Growth – Measurements should be plotted on the
appropriate growth chart for children with DS.
This will help in prevention of obesity and early
diagnosis of celiac disease and hypothyroidism.
2. Cardiac disease – All newborns should be evaluated
by cardiac ECHO for CHD in consultation with pediatric
cardiologist.
3. Hearing – Screening to be done in the newborn
period, every 6 months until 3 yrs of age and then
annually.
Management

39. 4. Eye disorders - An eye exam should be
performed in the newborn period or at least
before 6 months of age to detect strabismus,
nystagmus, and cataracts.
5. Thyroid Function – Should be done in
newborn period and should be repeated at
six and 12 months , and then annually.
6. Celiac Disease – Screening should begin at
2 yrs. Repeat screening if signs/Sx develop.

40. 7. Hematology – CBC with differential at birth to
evaluate for polycythemia as well as WBC.
8. Atlanto-axial instability – X ray for evidence of AAI
or sub-luxation at 3 to 5 years of age.
9. Alzheimer’s disease – Adult with a Down
Syndrome has earlier onset of symptoms. When
diagnosis is considered, thyroid disease and
possible depression should be excluded.

41. Median age of death has increased from 25 yrs in 1983
to 49 yrs in 1997, an average of 1.7 yrs increase per year.
Most likely cause of death is CHD, Dementia,
Hypothyroidism and Leukemia.
Improved survival is because of increased placements of
infants in homes and
changes in treatment for common causes of death.
Survival is better for males and blacks.
Mortality

42. May begin when a prenatal diagnosis is made.
Discuss the wide range of variability in
manifestation and prognosis.
Medical and educational treatments and
interventions should be discussed.
Initial referrals for early intervention, informative
publications, parent groups, and advocacy groups.
Counseling

46. Rare Trisomy
trisomy 14

47. Infant presented with low set ear , cleft lip , arm
and leg abnormalities ( unequal leg length)
Infant also diagnosed with VSD and jaundice at
birth

48. Trisomy 8 Mosaicism

49. Main features :
build:
Babies are born with a normal weight and length. T hey may
have
a short neck, occasionally with extra skin folds, and a long slim
body with a narrow chest, shoulders and pelvis, which may
become more apparent with age.
Limbs :
Stiff joints with a limited range of movement; clenched or
bent
fingers and/or toes; deep palm and sole creases; occasionally
underdeveloped nails; missing or small kneecaps (termed
‘patellae’).
Facial appearance :
A pear-shaped, bulbous nose with upturned nostrils, a
protruding lower lip and large ears.

50. Rare Trisomy
trisomy 9

51. Trisomy 9 is a chromosomal disorder caused by having three
copies (trisomy) of chromosome number 9.
It can appear with or without mosaicism. Characteristics
Symptoms vary, but usually result in dysmorphisms in the skull,
nervous system, and developmental delay. Dysmorphisms in the
heart, kidneys, and musculoskeletal system may also occur.
An infant with complete trisomy 9 surviving 20 days after birth
showed clinical features including a small face, wide fontanelle,
prominent occiput, micrognathia, low set ears, upslanting
palpebral fissures, high arched palate, short sternum,
overlapping fingers, limited hip abduction, rocker bottom feet,
heart murmurs and also a webbed neck.

52. Detection
Trisomy 9 can be detected prenatally with chorionic
villus sampling and cordocentesis, and can be
suggested by obstetric ultrasonography
Because trisomy 9 may appear with mosaicism, it is
suggested that doctors take samples from multiple
tissues when karyotyping for diagnosis

53. Trisomy16
Trisomy 16 is a chromosomal abnormality in which
there are 3 copies of chromosome 16 rather than two.
It is the most common trisomy leading to miscarriage
and the second most common chromosomal cause of
it, closely following X-chromosome monosomy.
Like most chromosomal abnormalities, trisomy 16
usually causes miscarriage in the first trimester of
pregnancy.

54. Trisomy 22
cat eye syndrome