3. DOWN SYNDROME
Most common
chromosomal disorder
INCIDENCE
If maternal age is <20 yrs
,Approximately 1 in 1550
live births,
But if maternal age is >45
yrs ,incidence is 1 in 25 live
births
4. Genetics
Trisomy 21 (47,XX, +21), - 94 %, The
frequency of trisomy increases with
increasing maternal age.
Robertsonian translocation involving
chromosome 21- Approx. 3-4 %, not related
to maternal age.
Trisomy 21 mosaicism – 1-2% cases
5.
6.
7.
8. Clinical Features
Head and neck
Flat facial profile
Up-slanting palpebral fissures
Epicanthal folds
Brushfield spots
Flat nasal bridge
Folded or dysplastic ears
Open mouth
Protruding tongue
Short neck
Excessive skin at the nape of
neck
Extremities
Short broad hands
Short fifth finger
Incurved fifth finger
Transverse palmer crease
Space between first and
second toe
Hyper flexibility of joints
9.
10.
11. Mental Retardation
Almost all DS babies have MR.
Mildly to moderately retarded .
Starts in the first year of life.
Average age of sitting(11 mon), and walking (26
mon) is twice the typical age.
First words at 18 months.
IQ declines through the first 10 years of age,
reaching a plateau in adolescence that continues
into adulthood.
12. Heart Disease
GI Abnormalities
50 % of Down Syndrome pts have heart disease
Atrioventricular septal defect
VSD
Secundum ASD
Mitral valve prolapse
Valvular malformation
GI abnormalities –in 5% cases of DS
Duodenal atresia or stenosis
Oesophageal atresia and intestinal stenosis
13. Hematologic disorders
The risk of leukemia is 1 to 1.5 percent.
65% of newborn have polycythemia resulting in
hypoglycemia.
Risk of AML ( ACUTE MEGAKARYOBLASTIC
LUEKEMIA )is also much higher than the general
population.
Transient leukemia.
14. Diagnosis
Prenatal screening
If no screening – It is recognized from the
characteristic phenotypic features.
Confirmed by Karyotype.
15. Mortality
Median age of death has increased from 25 yrs
to 49 yrs , 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.
17. KLINEFELTER SYNDROME
It is the state of male hypogonadism
due to 2 or more X chromosome with
1 or more y chromosome.
INCIDENCE : 1 in 2000 live male
births
KARYOTYPE: 82% have classical
47,XXY
15% mosaics , 46XY/47,XXY
Remaining polysomic individuals
18. cause
MEIOSIS 1
(GAMETOGENESIS)
NON DISJUNCTION
occurs when
homologous
chromosomes ( X and Y)
fails to separate and
producing a sperm with
extra X and Y
chromosome
19. Clinical features
Abnormally
increased distance
between pubic ramus
and sole of feet.
Lower body appears
abnormally
elongated also called
as EUNUCHOID
BODY HABITUS
20. CLINICAL FEATURES
Atrophied testes - testicular biopsy shows
atrophied hyalinised seminiferous tubules
with no spermatogenesis.
Lack of secondary sexual characteristics
Gynecomastia is seen
Mental intelligence is near normal
Greater the number of X chromosome
,lower is the level of intelligence
21. COMPLICATIONS
Infertility
20x increased risk of ca breast
Increased risk of germ cell tumor
Increased risk of autoimmune
diseases like SLE (SYSTEMIC
LUPUS ERYTHEMATOSUS)