10/22: Craniofacial mutations Flashcards
1/50 infants born with a genetic condition is attributed to
Single major mutation
Chromosome disorders
Aneuploidy, deletions
Single gene disorders
dominant, recessive, codominant
multifactorial gene diseases
multiple genes, gene environment
Aneuploidy
- aberration in chromosome #
- faulty segregation of chromosomes during mitosis/meiosis
- 1/400 infants
- Female meiosis I
down syndrome
- Full or partial extra copy of chrom 21
- 1 in 700 babies
- Most common chrom condition
95% of cases of down syndrome are
Nondisjunction
the only factor that has been linked to an increased chance of having a baby with Down syndrome resulting from
nondisjunction or mosaicism
maternal age
Down syndrome characteristics
- low muscle tone
- small stature
- cog delay
- transverse palmar crease
How can down syndrome affect patients?
- Heartburn wears on the enamel
- Sleep apnea
What 3 questions should you ask a patient with down syndrome?
- Heart defects
- Spinal problems
- Seizures
Chromosomal rearrangements
chromosome breakage or recomb btwn mispaired chromosomes during meiosis
Cri-du-Chat Syndrome
- High-pitched cry
- sounds like a cat
- 1 in 20-50,000
Cri-du-Chat
- affects intellectual and development
- microcephaly
- low birth weight
- hypotonia
- transverse palmar
- heart defects
Facial features of Cri du chat syndrome
- hypertelorism (wideset eyes)
- low set ears
- micrognathia
- moon facies
- epicanthal folds
- broad nasal bridge
- palpebral fissures
Dominant single gene mutation
Heterozygotes, a single copy of the mutation
- severe dominant often caused by new mutation
Recessive single-gene mutation
homozygotes
Multifactorial diseases (polygenic/complex)
not a single mutation, interacting genes and environment risk factors
- allergies
- heart disease
There are multiple neural crests; why is the palate a common birth defect but not others?
Other cleft defects are not compatible with life
What do cleft lip and palate deformities usually affect in the dentition?
laterals and canines (primary palate)
What is palatogenesis, and why is it important?
Formation of the secondary plate, separates nasal cavity from oral cavity
Palatogenesis: Week 7
growth - median palatal process (medial nasal and frontonasal processes) - forms the primary palate
Palatogenesis: Week 8
Elevation:
The nasal septum is derived from the frontonasal prominence
Palatal shelves are derived from the maxillary process of the first pharyngeal arch
Palatogenesis: Week 9
Fusion: The secondary palate is formed - separates the nasal cavity from oral cavity
What is the secondary palate needed for?
-swallowing
-taste
-vomiting
-breathing
-speaking
CPO is a result of (3)
failed palatogenesis:
-Failure in growth (7)
-Failure in elevation (8)
-failure in fusion (9)
CP in CL/CP (cleft lip with cleft palate)
Cleft palate is a secondary defect from a failed lip fusion (week 4-7)
Cleft palate a phenotype of a known syndrome accounts for
30% of cases
Some of identified causes for cleft palare
Environmental
- alcohol
- phenytoin
- retinoic acid
- radiation (X-rays)
- TCDD…
Nutritional / metabolic
- low methionine
- low folic acid
- maternal DM
- hypervit. A
Genetic 350+: Mendelian disorders, chromosomal aberrations
Cleft lip and palate causes
● babies: failure of suckling, later eating
problems
● dental defects, malocclusion
● speech difficulties
● infectious complications, hearing
impairment
Problem caused by therapy of cleft palate
Defective maxillary growth
