14. congenital anomalies

Question 1

percentage breakdown of what congenital anomalies are caused

Answer 1

single gene disorders - 7.5%
chromosomal - 6%
multifactorial - 20%
teratogens - 2 to 3%
unknown cause - over 50%

Question 2

major congenital anomaly

and example

Answer 2

a structural abnormality present at birth which has a significant effect on function or social acceptability

eg. ventricular septal defect
cleft lip

Question 3

minor congenital abnormality

and example

Answer 3

a structural abnormality present at birth which has minimal effect on clinical function but may have a cosmetic impact

eg, prearticular pit

Question 4

developmental variant and example

Answer 4

a cosmetically and functionally insignificant structural deviation from the usual, of prenatal origin and usually familial

eg. fifth finger clinodactylyl

Question 5

what are the different types of structural abnormalities that occur during fetal development

Answer 5

deformation
disruption
malformation

Question 6

explain disruption

Answer 6

the damage of a structure or organ that was previously

Question 7

explain deformation

Answer 7

alterations in the shape or form of a structure due to mechanical forces applied externally.

Question 8

malformation

Answer 8

a morphological anomaly resulting from an intrinsically abnormal development process

Question 9

malformation sequence

Answer 9

the initial abnormality disrupts normal embryonic development,
leading to a cascade of secondary anomalies or abnormalities in related structures or systems.

Question 10

examples of Malformation sequences

Answer 10

Potters sequence
Pierre Robin sequence

Question 11

clinical features of Pierre-Robin sequence

Answer 11

cleft palate
small chin
glossoptosis (tongue positioned lower or further back in mouth)

Question 12

Potter sequence

Answer 12

lack of amniotic fluid surrounding developing foetus

symptoms:
amniotic leak
non- functioning kidneys
absent kidneys
small chin
cleft palate
limb contractures
hypoplastic lungs

Question 13

give an example of malformation syndrome - chromosomal

and symptoms

Answer 13

Patau syndrome - trisomy 13

symptoms:
- single small forebrain
- cleft lip and palate
- congenital heart disease
- absent eyes

Question 14

give an example of malformation syndrome - single gene disorder
and symptoms

Answer 14

Van der Woude syndrome

symptoms:
- predisposition to cleft lip and palate
- lower lip pits

Question 15

give an example of malformation syndrome - Teratogen

clinical features

Answer 15

femoral aplasia/ hypoplasia
- common in children with diabetic mothers

symptoms:
- abnormal lower spine
- talipes
- cleft palate
- unusual facial appearance

Question 16

what causes neural tube defect/ spinal bifida

Answer 16

failure of the closure of the neural tube

Question 17

what is the neural tube

Answer 17

the precurser of both the brain and the spinal chord, it develops at 4 weeks gestation

Question 18

what are symptoms of a mild case of spinal bifida

Answer 18

hairy patch over lumbar spine

Question 19

what is the most severe result of spinal bifida

Answer 19

absence of the cortical brain

Question 20

if a couple has had a child with a NTD are they likely to have another child with a neural tube defect

Answer 20

their chance of having another child with a NTD is approximately 4%

Question 21

what can be taken to reduce the incidence of NTDs

Answer 21

folic acid supplements during pregnancy

Question 22

cleft lip/cleft palate

Answer 22

common congenital anomaly
usually isolated with no family

Question 23

what can cleft lip/ cleft palate be associated with

Answer 23

chromosomal anomalies
single gene disorders
teratogens

Question 24

developmental genetics

Answer 24

the study of genetic processes with control embryogenesis

Question 25

why do we use drosophilia (house flies) and mouse genetics in studies

Answer 25

the human equivalents of genes shown to be important in mouse or drosophila embryonic development are mutated in some children with special congenital anomalies
several important gene families have been identified in this way

Question 26

what are segmentation genes

Answer 26

they were first discovered in drosphila by study of spontaneous induced mutant phenotypes with abnormalities of body segments

Question 27

what are the three particular mutant group recognized of segmentation genes

Answer 27

gap mutants
pair-rule mutants
segment- polarity mutants

Question 28

Waardenburg syndrome clinical symptoms

Answer 28

deafness
different coloured irises
white hair patches

Question 29

clinical features of Aniridia

Answer 29

absent iris
gluacoma
visual impairment

Question 30

single transduction genes

Answer 30

the regulatory process for cell growth and differentiation

Question 31

what can pathogenic variants in the genes involved cause

Answer 31

cancer and/ or developmental abnormalities

Question 32

what is the difference between gain of function and loss of function pathogenic variant

Answer 32

gain of function is likely to cause tumurs
loss of function will cause Hirschsprung disease

Question 33

fibroblast growth factors

Answer 33

they are growth stimulators
they bind to specific receptors which lie across the cell membrane

Question 34

what is craniosynostosis

Answer 34

the fusion of skull bones and syndactyly

Question 35

hydatidiform mole

Answer 35

condition where you have uncontrollable growth in the placenta

Question 36

partial mole

Answer 36

this occurs in the triploidy of paternal origin. 69, XYY
the foetus rarely survives to term

Question 37

complete mole

Answer 37

these have 46 chromosomes which are exclusively paternal in origin
there is no embryonic development

Question 38

identical (monozygotic) twins

Answer 38

they originate from a single conception and are genetically identical

Question 39

Non- identical (Dizygotic) twins

Answer 39

originate from two separate conceptions, can be of different sex and are no more closely related genetically than brothers and sisters