Down Syndrome and Klinefelter's syndrome are chromosomal disorders. Down Syndrome is caused by trisomy of chromosome 21 and is characterized by distinctive facial features and cognitive impairment. Klinefelter's syndrome affects males and is caused by one or more extra X chromosomes, leading to hypogonadism and reduced masculine features. Both conditions can be detected prenatally by techniques like amniocentesis.

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2. • To explain Down’s syndrome
• To explain Klinefelter’s syndrome
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3. • Disorders related with human chromosomal
abnormalities.
• Structural abnormalities
• Numerical abnormalities
Euploidy
 Aneuploidy: Trisomy
Autosomal :
Down’s syndrome
Sex chromosomal:
Klinefelter’s syndrome
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4.  95% -trisomy 21= 47 chromosome
Meiotic non disjunction of 21 chromosome in ovum
Frequency: is related to maternal age
• 1/1550(in <20 years female)
• 1/25(in >45 years female)
• overall 1/750 new borns
 4%-Robertsonian translocation
 1%-Mitotic non disjunction,Mosaics:46 and 47
mixture
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6. • Flat facial profile, flat nasal
bridge
• Oblique palpebral fissures and
epicanthic folds
• Protruding tongue, macroglossia
near tonsils
• Short neck and microgenia
• Muscle hypotonic
• Leading cause of severe mental
retardation Epicanthic folds
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7. Epicanthic
folds
Simian
crease
Umbilical
hernia
Predisposition
to leukemia
hypotonia
Gap between first and second toe
Intestinal
stenosis
Congenital
heart disease
Abundant neck skin
Mental retardation
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8. • Congenital heart diseases (40%):
– Defects of endocardial cushion
– Atrial/ventricular septal defects
– Ostium primum
– Atrio-ventricular valve malformation
• Acute leukemia(ALL/AML)
• Alzheimer’s disease (in most patient>40 yrs)
• Abnormal immune responses: lung infection and
thyroid autoimmunity
• Hyperextensibility of joint
• Sterile males
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9. • Amniocentesis, Chorionic villus sampling,
Percutaneous umbilical blood sampling
• Ultrasound imaging
• With improved medical care-Median age=47
yrs
Ultrasound of fetus with Down
syndrome showing a large
bladder
Enlarged NT and absent nasal
bone in a fetus at 11 weeks
with Down syndrome
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10. Male Hypogonadism that occurs when
there are 2 or more X-chromosomes
and 1 or more Y-chromosomes.
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11. • Incidence: 1 in 660 male births
• 90% - 47,XXY : meiotic non-disjunction of
germ cells
• 15% mosaics, usually 46,XY/47,XXY
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12. • Uneven dosage compensation during X-
inactivation
• Androgen receptor genes with inactivation of
short sensitive CAG repeats and expression of
long CAG repeats Hypogonadism
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13. • Hypogonadism and long lower extremities
• Deficient male secondary sexual characters
 Small penis and testis
 Poor beard growth
• Female characters
 Gynaecomastia
 Narrow shoulder, wide hip
 Female type pubic hair pattern
 Absence of facial baldness
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15. • Mental retardation unusual,IQ level is below
normal
• Increased incidence of type 2 diabetes
• Higher risk of breast cancer(20X)
• Higher risk of extragonadal germ cell tumor
and autoimmune diseases such as SLE
• Prone to osteoporosis and bone fractures
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16. • Rarely diagnosed before puberty because
testicular abnormality does not appear before
puberty
• Presence of Barr body
• Increased lower extremities
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17. • Testosterone replacement therapy
• Breast tissue removal
• Speech and physical therapy
• Fertility treatment: intra cytoplasmic sperm
injection
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18. • Down Syndrome and klinefelters syndrome are
common chromosomal disorders.
• Down syndrome is due to trisomy of chromosome
21.
• Klinefelters syndrome is due to extra X chromosome
in male.
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19. • Robin’s Basis of Pathology 9th edition
• Langman’s Medical Embryology 12th edition
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