Year 1 Med School Teratology Slides Learning

Congenital Disease

1. TeratologyTeratology

2. Birth DefectsBirth Defects

Teratology is the study of congenital anomalies or Teratology is the study of congenital anomalies or
birth defects.birth defects.

Birth defects are leading cause of infant mortality.Birth defects are leading cause of infant mortality.
> 20 % of infant deaths in north america, % rises > 20 % of infant deaths in north america, % rises
with increasing age.with increasing age.

3. Birth DefectsBirth Defects

Maybe structural, functional, metabolic, Maybe structural, functional, metabolic,
behavioural, or hereditary.behavioural, or hereditary.

Some congenital defects are not detected at birth Some congenital defects are not detected at birth
but are found later in life like congenital but are found later in life like congenital
dislocation of hip, patent ductus arteriosus etc.dislocation of hip, patent ductus arteriosus etc.

4. Birth DefectsBirth Defects
UnilateralUnilateral
Cleft lipCleft lip
BilateralBilateral
Cleft lipCleft lip
Cleft lipCleft lip
and palateand palate

5. Birth DefectsBirth Defects

6. Birth DefectsBirth Defects

7. Birth DefectsBirth Defects

8. Birth DefectsBirth Defects

9. Clarification of TermsClarification of Terms

MalformationMalformation: Morphological : Morphological
defect of an organ or of part of defect of an organ or of part of
the body due to intrinsic the body due to intrinsic
abnormal development such as abnormal development such as
chromosomal defects.chromosomal defects.

DisruptionDisruption: Morphological : Morphological
defect due to extrinsic defect due to extrinsic
breakdown of a normal breakdown of a normal
developmental process like developmental process like
amelia amelia due to thalidomide. due to thalidomide.
AmeliaAmelia

10. Clarification of TermsClarification of Terms

DeformationDeformation: An : An
abnormal form of an abnormal form of an
organ or part of the body organ or part of the body
due to mechnical forces due to mechnical forces
like like club footclub foot or spina or spina
bifida etc.bifida etc.

DysplasiaDysplasia: An abnormal : An abnormal
organisation of cells into organisation of cells into
an organ or tissue like an organ or tissue like
cong. ectodermal cong. ectodermal
dysplasiadysplasia
Club footClub foot

11. Causes of Birth DefectsCauses of Birth Defects

Causes of most anomalies are unknown (50/60%)Causes of most anomalies are unknown (50/60%)

10/20 % are due to chromosomal or gene defects10/20 % are due to chromosomal or gene defects

7/10 % are due to environmental factors7/10 % are due to environmental factors

20 to 25 % are due to multifactorial inheritance.20 to 25 % are due to multifactorial inheritance.

Broadly classified into: Broadly classified into:
(1) Genetic factors (1) Genetic factors
(2) Environmental factors such as drugs and (2) Environmental factors such as drugs and
infections like German measles, syphilis, AIDSinfections like German measles, syphilis, AIDS

12. Teratogens and Stages of EmbryosTeratogens and Stages of Embryos

13. Genetic CausesGenetic Causes
1. Alterations in chromosome (ch) 1. Alterations in chromosome (ch)
morphologymorphology: :
(i) Cri du chat syndrome due to deletion (i) Cri du chat syndrome due to deletion
of short arm of ch 5.of short arm of ch 5.
(ii) (ii) Turner’s syndromeTurner’s syndrome due to absence of due to absence of
one X chromosome one X chromosome
(iii) Down’s syndrome due to (iii) Down’s syndrome due to
translocation of chromosome 21 with translocation of chromosome 21 with
13-15 chromosomes.13-15 chromosomes.
Turner’s syndromeTurner’s syndrome

14. Genetic CausesGenetic Causes
2. 2. Alteration in no. of chromosomeAlteration in no. of chromosome::
(i) Klinefelter’s syndrome 47 (XXY) (i) Klinefelter’s syndrome 47 (XXY)
(ii) Down’s syndrome 47 (Trisomy (ii) Down’s syndrome 47 (Trisomy
21) 21)
(iii) XXX(iii) XXX
Down’s syndromeDown’s syndrome

15. Genetic CausesGenetic Causes
3. Mutant Genes3. Mutant Genes: :
(I) Auto Dominant eg (I) Auto Dominant eg
polydactaly, achondroplasia polydactaly, achondroplasia
(ii) Auto Recessive eg albinism (ii) Auto Recessive eg albinism
(iii) Sex-linked eg haemophilia, (iii) Sex-linked eg haemophilia,
colour blindness etc.colour blindness etc.
PolydactalyPolydactaly

16. Nondysjunction of Chromosomes

17. Environmental Factors Environmental Factors
A. Intrinsic Factors:A. Intrinsic Factors:
Affect through placental barrier Affect through placental barrier
1.1. Maternal viral infections like Maternal viral infections like
German measles may cause German measles may cause
congenital cataract, deafness and congenital cataract, deafness and
mental retardation mental retardation
2.2. Toxoplasmosis may produce Toxoplasmosis may produce
hydrocephalushydrocephalus..
3.3. Syphilis may cause cleft palate, Syphilis may cause cleft palate,
cleft lip, deafness, spina bifida.cleft lip, deafness, spina bifida.
HydrocephalusHydrocephalus

18. Environmental Factors Environmental Factors
4. Drugs: 4. Drugs:
(a) Thalidomide causes limb (a) Thalidomide causes limb
anomalies like amelia, anomalies like amelia,
phocomelia phocomelia
(b) Aminopterin is sometimes (b) Aminopterin is sometimes
used as an abortion drug.It may used as an abortion drug.It may
cause anaencephaly, cause anaencephaly,
hydrocephalus etchydrocephalus etc
(c) Steroids may cause cleft (c) Steroids may cause cleft
palate.palate. PhocomeliaPhocomelia

19. Environmental Factors Environmental Factors
5.5. Diabetes mellitus causes abortion, neonatal Diabetes mellitus causes abortion, neonatal
deaths and big baby.deaths and big baby.
6.6. Nutrition: Lack of Vitamin D produces rickets , Nutrition: Lack of Vitamin D produces rickets ,
maternal iodine deficiency gives birth to cretinn. maternal iodine deficiency gives birth to cretinn.
7.7. Hypoxia produces smaller babies like mothers Hypoxia produces smaller babies like mothers
at high altitude give birth to smaller babies.at high altitude give birth to smaller babies.

20. Environmental Factors Environmental Factors
8.8. maternal antibodies like Rh antibody and maternal antibodies like Rh antibody and
thyroid antibodies affect the child. Rh negative thyroid antibodies affect the child. Rh negative
mother will produce Rh antibodies with Rh + mother will produce Rh antibodies with Rh +
child. Subsequent babies are worst affected, child. Subsequent babies are worst affected,
erythroblastosis foetaliserythroblastosis foetalis

21. B. Extrinsic Factors:B. Extrinsic Factors:
1. Abnormal implantation of 1. Abnormal implantation of
blastocyst near internal os of blastocyst near internal os of
cervix produces placenta cervix produces placenta
praevia.praevia.
2. Fetal adhesions to amniotic 2. Fetal adhesions to amniotic
membrane by fibrous bands membrane by fibrous bands
may amputate a limb.may amputate a limb.
3. Hydramnios may produce 3. Hydramnios may produce
anencephaly.anencephaly.
Environmental FactorsEnvironmental Factors

22. 4. Radiation by x-ray, radioisotopes etc may produce 4. Radiation by x-ray, radioisotopes etc may produce
fetal malformations and leukaemia etc.fetal malformations and leukaemia etc.
5. Other factors like maternal age , social status and 5. Other factors like maternal age , social status and
season of conception and birth also affect child season of conception and birth also affect child
growth;growth;
Psychology of mother during conception is also Psychology of mother during conception is also
important.important.
Environmental FactorsEnvironmental Factors

23. Important FactorsImportant Factors

Stage of development of embryo when the Stage of development of embryo when the
teratogen acts: 3rd to 8teratogen acts: 3rd to 8
thth
week is most vulnerable, week is most vulnerable,
cataract in 6cataract in 6
thth
week, deafness in 9 week, deafness in 9
thth
week, cardiac week, cardiac
defects in 5defects in 5
thth
to 10 to 10
thth
week. week.

Mode of action of teratogen on the tissues of the Mode of action of teratogen on the tissues of the
embryo: Action on organisers or direct actionembryo: Action on organisers or direct action

Role of genotype on the action of teratogens: Role of genotype on the action of teratogens:
Abnormal chromosomes or genes aid the action Abnormal chromosomes or genes aid the action
of teratogens to produce anomalies.of teratogens to produce anomalies.