Also named
Down’s Syndrome
（ 21 trisomy）
One pair of chromosome
21 was seen in peripheral
lymphocytes of normal
person
trisomy of chromosome 21
was seen in the peripheral
lymphocytes of patient
with 21-trisomy
Q221 trisomy will
cause the phenotype
of 21-trisomy
Schematic digram of chromosome 21
只需 Q221 三体即可导致 21 三体综合征表型
Pathogenesis of various
type of 21 trisomy
? Standard type (47,XY/XX,+21)
? masaicism（ 46 / 47 + 21）
? Translocation（ eg,46,-13,+t(13q;21q）
Karyotype of various type of 21-trisomy
21 21
21monosomy 21-trisomy
Pathogenesis of standard type 21-trisomy:disjunction of
chromosome 21 during miosis
Disjunction of
chromosome 21
21 21 21
21 21 Germ cells21 21
21 21 0 gamete 21 21
21 21 21 oosperm
miosis
21-trisomy
cell series
Normal cell
series
3条 21 号染色体
2条 21 号染色体
Karyotype of
mosaicism 21-trisomy
mitosis
21 21 Oosperm
21 21 21 21 First generation
21 21 21 21 21 2121 21 seocnd generation
Disjunction of
chromosome 21
during mitosis
Pathogenesis of mosaicism 21-trisomy
Nondisjunction in early cell division of a normal zygote
Translocation of long
arm of chromosome
21 to chromoxome 14
Example of translocation of 21-trisomy
14q
14p
21q
21p
Pathogenesis of translocation in 21-trisomy
21q
21p
14q
14p
Breakage at centromere
14q
21q
Reunite of the
two long arms
14p
21pReunite of the
two short arms
Genetic carrier
in the parent normal parent
21
14
21
14
21
14
21
14
21
14
21
14 14
21
14 21
Gamete
(t14q21q)
21
14
normal
21
14
carrier
21
14
21-trisomy
21
14
21-
monosomy
21
14
14-trisomy
21
14
14-
monosomy
Still birthPathogenesis of translocation in 21-trisomy
A kindred of translocation 21-trisomy
Translocation of part
of one chromosome
21 to another
chromosome 21
Translocation of chromosome 21
Clinical Manifestations
Major Clinical Manifestations
? Charcteristic Face
? Growth retardation
? Multiple malformations
? Mental retardation
Epicanthal folds
slanged upwardhypertelorism
flattened bridge
Opening mouthLow set ears
Major characteristics of the face
Epicanthal folds
slanged upwardhypertelorism
flattened bridge
Open mouth with
macroglosis
Major characteristics of the face
Major characteristics of the face
Low set ear
Major characteristics of the face
Epicanthal folds
slanged upwardhypertelorism flattened bridge
Low set ear with
malformation
Masaicism of 21-trisomy with approximate phenotype of normal person
Simian line of the palm
Normal palmar crease
Simian line
atd angle
normal simian line
Schematic diagram of palmar simian line
widening between toes
deep crease
、Deep crease
Widening
between toes
Simian
line
curving 5th finger
Short second segment
Simian
line
Short second segment
Relax of
abdominal muscle
Relax of hip joints that allows overextension
floppy infant syndrome’s clinical
manifestations
Auricle malformation
macroglossia
iris speckling
Major clinical manifestations
congenital heart defects was seen in
30%～ 50% of the patients
Higher incidence of various infection
and leukemia
Early onset of senile dementia
Laboratory and adjunct
examinations
排列
采血
组织培养 Ch
rom
osom
e an
aly
sis
细胞来源
固定
分裂相 摄影
Chromosome 21
Schematic diagram of G-band karyotype
Photo of G-band karyotype shows three
chromocome 21
Schematic diagram of the
previous photo
Diagnosis based on clinical characteristics
and karyotype analysis
Therapy, mainly symptomatic,
Adjunct with small dose of thyroxin and
nutrients supplement
Prevention
Years of age
母亲育龄 > 35 岁者应
进行产前诊断
Incidence of 21-trisomy is closely associated with age of the pregnant woman,
prenatal diagnosis should be performed for pregnant woman aged older than
35 years
平衡易位类型 子代为 21－ 三体的机率（％）
T ( Dq 21 q)
T ( 21q 22 q)
T ( 21q 21 q)
父
母
父
母
父
母
5
10
< 3
7
100
100
母明显高于父
Chance of 21-trisomy in the offspring born from
translocation carrier of parents
First trimester screening includes:
NT
PAPP-A,
hCG
uE3
with false positive rate of only 5%
Patient shows positive screening result：
? Chorionic cells
? amniotic fluid
? nucleated cells from pregnant woman
Karyotype
analysis
“FISH” and specific cCNA can be used to raise the
positive rate
Down’s Syndrome
（ 21 trisomy）
One pair of chromosome
21 was seen in peripheral
lymphocytes of normal
person
trisomy of chromosome 21
was seen in the peripheral
lymphocytes of patient
with 21-trisomy
Q221 trisomy will
cause the phenotype
of 21-trisomy
Schematic digram of chromosome 21
只需 Q221 三体即可导致 21 三体综合征表型
Pathogenesis of various
type of 21 trisomy
? Standard type (47,XY/XX,+21)
? masaicism（ 46 / 47 + 21）
? Translocation（ eg,46,-13,+t(13q;21q）
Karyotype of various type of 21-trisomy
21 21
21monosomy 21-trisomy
Pathogenesis of standard type 21-trisomy:disjunction of
chromosome 21 during miosis
Disjunction of
chromosome 21
21 21 21
21 21 Germ cells21 21
21 21 0 gamete 21 21
21 21 21 oosperm
miosis
21-trisomy
cell series
Normal cell
series
3条 21 号染色体
2条 21 号染色体
Karyotype of
mosaicism 21-trisomy
mitosis
21 21 Oosperm
21 21 21 21 First generation
21 21 21 21 21 2121 21 seocnd generation
Disjunction of
chromosome 21
during mitosis
Pathogenesis of mosaicism 21-trisomy
Nondisjunction in early cell division of a normal zygote
Translocation of long
arm of chromosome
21 to chromoxome 14
Example of translocation of 21-trisomy
14q
14p
21q
21p
Pathogenesis of translocation in 21-trisomy
21q
21p
14q
14p
Breakage at centromere
14q
21q
Reunite of the
two long arms
14p
21pReunite of the
two short arms
Genetic carrier
in the parent normal parent
21
14
21
14
21
14
21
14
21
14
21
14 14
21
14 21
Gamete
(t14q21q)
21
14
normal
21
14
carrier
21
14
21-trisomy
21
14
21-
monosomy
21
14
14-trisomy
21
14
14-
monosomy
Still birthPathogenesis of translocation in 21-trisomy
A kindred of translocation 21-trisomy
Translocation of part
of one chromosome
21 to another
chromosome 21
Translocation of chromosome 21
Clinical Manifestations
Major Clinical Manifestations
? Charcteristic Face
? Growth retardation
? Multiple malformations
? Mental retardation
Epicanthal folds
slanged upwardhypertelorism
flattened bridge
Opening mouthLow set ears
Major characteristics of the face
Epicanthal folds
slanged upwardhypertelorism
flattened bridge
Open mouth with
macroglosis
Major characteristics of the face
Major characteristics of the face
Low set ear
Major characteristics of the face
Epicanthal folds
slanged upwardhypertelorism flattened bridge
Low set ear with
malformation
Masaicism of 21-trisomy with approximate phenotype of normal person
Simian line of the palm
Normal palmar crease
Simian line
atd angle
normal simian line
Schematic diagram of palmar simian line
widening between toes
deep crease
、Deep crease
Widening
between toes
Simian
line
curving 5th finger
Short second segment
Simian
line
Short second segment
Relax of
abdominal muscle
Relax of hip joints that allows overextension
floppy infant syndrome’s clinical
manifestations
Auricle malformation
macroglossia
iris speckling
Major clinical manifestations
congenital heart defects was seen in
30%～ 50% of the patients
Higher incidence of various infection
and leukemia
Early onset of senile dementia
Laboratory and adjunct
examinations
排列
采血
组织培养 Ch
rom
osom
e an
aly
sis
细胞来源
固定
分裂相 摄影
Chromosome 21
Schematic diagram of G-band karyotype
Photo of G-band karyotype shows three
chromocome 21
Schematic diagram of the
previous photo
Diagnosis based on clinical characteristics
and karyotype analysis
Therapy, mainly symptomatic,
Adjunct with small dose of thyroxin and
nutrients supplement
Prevention
Years of age
母亲育龄 > 35 岁者应
进行产前诊断
Incidence of 21-trisomy is closely associated with age of the pregnant woman,
prenatal diagnosis should be performed for pregnant woman aged older than
35 years
平衡易位类型 子代为 21－ 三体的机率（％）
T ( Dq 21 q)
T ( 21q 22 q)
T ( 21q 21 q)
父
母
父
母
父
母
5
10
< 3
7
100
100
母明显高于父
Chance of 21-trisomy in the offspring born from
translocation carrier of parents
First trimester screening includes:
NT
PAPP-A,
hCG
uE3
with false positive rate of only 5%
Patient shows positive screening result：
? Chorionic cells
? amniotic fluid
? nucleated cells from pregnant woman
Karyotype
analysis
“FISH” and specific cCNA can be used to raise the
positive rate
