Lecture 2: Genetic Syndromes

Question 1

Prevalence of clefts: How many babies are born with clefts?

Answer 1

• 1:700 live births (over 5,000) in US each year
• between 1/5000 and 1/1000 for cleft lip and/or cleft
  palate, and about 1/2500 for cleft palate alone

Question 2

Prevalence of clefts: What groups are clefts more common?

Answer 2

more common among Asians (1:500) and certain groups of American Indians (1:300) than among Caucasians (1:800)

Question 3

Prevalence of clefts: What group are clefts least common?

Answer 3

occur less frequently among African-Americans (1:2000)

Question 4

Prevalence of clefts: What gender is more likely to have a cleft lip and cleft palate together (ratio)?

Answer 4

Cleft lip and cleft palate together are more common in boys - 3:2 ratio

Question 5

Research findings

Answer 5

• Cleft palate may result from a combination of genetic and environmental factors (NIH, 1997)
• Scientists have identified not just a single gene, but a genetic circuit, that when broken, causes cleft palate in
  newborn mice (NIH, 1997)
• Familial patterns and gene mapping involved in oral- facial clefts (Marazita, 1999)
• Gene ID’s shown to contribute to syndromic & non- syndromic CP/L

Question 6

If neither parent has a cleft than the inheritance is either ________ or _________.

Answer 6

If neither parent has a cleft than the inheritance is probably either multifactorial or recessive and these are usually not distinguishable (multifactorial=combination of genes and environment)

Question 7

What is the percentage of having another child with a cleft if the first child is born with a cleft?

Answer 7

Approximately 3-5% chance of having another similarly affected (risk increases more if have more than 1 affected child)

Question 8

Multifactorial hereditary risks include:

Answer 8

• Recessive inheritance
• Autosomal dominant
• If it can be established that there are no other affected relatives, the risk to siblings (2.2%) is less than the overall risk (4%)
• Recurrence also influenced by how severe the cleft is: 5.6% for bilateral CP/L, 4.1% for unilateral CP/L and 2.6% for CL without CP

Question 9

Syndromes are more common in ___________ than in ___________.

Answer 9

Syndromes are more common in CP alone than in CL with or without CP.

Question 10

Clefts can occur with what syndromes?

Answer 10

• Stickler Syndrome
• Treacher Collins
• CHARGE
• Pierre Robin
• DeGeorge (22-q deletion)
• Goldenhar
• Crouzon
• more listed in PPT