Teratology Causes of congenital malformations

Teratology

• Teratology

• Causes of congenital malformations:

• (a) Genetic factors: chromosomal abnormalities

• (b) Environmental factors: drugs, viruses

• Types of chromosomal abnormalities:

• (a) Numerical

• (b) Structural

Changes in the number of chromosomes:

• Changes in the number of chromosomes:

• Polyploidy
• Somatic cells contain multiples of haploid number of chromosomes
• 3n, 4n, 5n etc.
• Aneuploidy (Heteroploidy)
• Deviation from the diploid number of chromosomes
• 2n + 1, 2n -1 etc.

Failure of pulling apart of 2 chromatids to opposite ends after metaphase stage of mitosis.

• Failure of pulling apart of 2 chromatids to opposite ends after metaphase stage of mitosis.

• Reduplication of chromosomes without dissolving of nuclear membrane.

• Failure of cytoplasmic division.

Autopolyploidy: even-numbered multiples of haploid number of chromosomes. e.g.-

• Autopolyploidy: even-numbered multiples of haploid number of chromosomes. e.g.-

• (a) Tetraploidy (23x4 or 92 chromosomes)

• (b) Hexaploidy (23x6 or 138 chromosomes)

• (c) Octaploidy (23x8 or 184 chromosomes)

• etc.

2. Allopolyploidy: odd-numbered multiples of haploid number of chromosomes. e.g.-

• 2. Allopolyploidy: odd-numbered multiples of haploid number of chromosomes. e.g.-

• (a) Triploidy (23x3 or 69 chromosomes)-commonest

• (b) Pentaploidy (23x5 or 115 chromosomes)

• (c) Heptaploidy (23x7 or 161 chromosomes)

• etc.

Non-dysjunction: failure of separation of chromosomes during cell division.

• Non-dysjunction: failure of separation of chromosomes during cell division.

• Formation of 2 types of gametes (both abnormal)

• Fusion of either of these abnormal gametes with a normal gamete can result in trisomy or monosomy

• May involve autosomes or sex chromosomes

Presence of 3 copies of a chromosome

• Presence of 3 copies of a chromosome

• Trisomy of Autosomes (13,18,21)

• Trisomy of Sex Chromosomes (XXX, XXY)

Trisomy 13 or D-trisomy (Patau syndrome)

• Trisomy 13 or D-trisomy (Patau syndrome)

• Trisomy 18 or E-trisomy (Edward syndrome)

• Trisomy 21 or G-trisomy (Down syndrome)

1st described by Bartholin (1657) & redefined by

• 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)

Mental deficiency

• Mental deficiency

• Low birth weight

• Abnormal development

• of frontal lobe

• Absence of corpus callosum

• Hypoplasia of cerebellum

• Sloping forehead

• Scalp defects

Chromosomal complement: 47,XX,+18 (female) or

• Chromosomal complement: 47,XX,+18 (female) or

• 47,XY,+18 (male)

• Phenotype: Male or female

• Incidence: 1:8000

Mental deficiency

• Mental deficiency

• Growth retardation

• Prominent occiput with elongated head

• Webbing of the neck

• Short sternum

• Micrognathia

Chromosomal complement: 47,XX,+21 (female) or

• Chromosomal complement: 47,XX,+21 (female) or

• 47,XY,+21 (male)

• Phenotype: Male or female

• Incidence: 1:800 (increases with the age of

• mother)

Short height

• 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

1. Essentials of Anatomy for Dentistry Students,1st Edition.

• 1. Essentials of Anatomy for Dentistry Students,1st Edition.

• 2. Langman’s Medical Embryology,11th Edition.

• 3. Human Embryology, 5th Edition.

1. Patau syndrome is associated with trisomy of chromosome:

• 1. Patau syndrome is associated with trisomy of chromosome:

• a) 13

• b) 15

• c) 18

• d) 21

2. Rocker-bottom heel is associated with:

• 2. Rocker-bottom heel is associated with:

• a) Patau syndrome

• b) Edward syndrome

• c) Down syndrome

• d) None of the above

3. Brushfield spots is a characteristic feature of:

• 3. Brushfield spots is a characteristic feature of:

• a) Patau syndrome

• b) Edward syndrome

• c) Down syndrome

• d) None of the above

4. All of the following are trisomy of autosomes except:

• 4. All of the following are trisomy of autosomes except:

• a) Edward syndrome

• b) Klinefelter syndrome

• c) Down syndrome

• d) Patau syndrome

5. All of the following are examples of autopolyploidy except:

• 5. All of the following are examples of autopolyploidy except:

• a) Triploidy

• b) Tetraploidy

• c) Hexaploidy

• d) Octaploidy