genetic conditions and birth defects
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GENETIC CONDITIONS AND BIRTH DEFECTS
Camila Vieira Shanahan, MS, CGCGenetic CounselorFullerton Genetics CenterFebruary 17, 2012
Outline Prenatal Exposures Types of Genetic Conditions
Multifactorial disorders Chromosomal disorders Single gene disorders Mitochondrial disorders
Genetics Clinic
What are birth defects? Birth defects are defined as
abnormalities of structure, function, or body metabolism that are present at birth.
These abnormalities lead to mental or physical disabilities or are fatal.
There are more than 4,000 different known birth defects ranging from minor to serious.
With every pregnancy, the chance for a baby to be born with a birth defect is…
3-5%
Pregnancy Timeline
MAINTAINING A HEALTHY LIFESTYLE IS IMPORTANT DURING PREGNANCY
Which of the following can cause more harm to a fetus?
1. Cigarettes2. Crack/Cocaine3. Heroin4. Alcohol
“Alcohol causes more damage to the developing fetus than any other substance, including marijuana, heroin, and cocaine.”
Institute of Medicine, 1996
Effects of Alcohol Consumption of
alcohol during pregnancy can have devastating effects on the baby
No amount of alcohol is okay
Fetal Alcohol Syndrome The name commonly given to the group of
physical features found in children exposed to alcohol during pregnancy
Common features include: Classic facial features Growth problems in both weight and height Heart, liver, and kidney problems Vision and hearing problems Difficulties with learning, attention, memory,
and problem solving
Characteristic FAS Facial Features
Source: www.come-over.to/FASCRC/
Source: www. niaaa.nih.gov/
Fetal Alcohol Syndrome Approximately 1 in
every 100 children born have some effects of alcohol
The leading known preventable cause of mental retardation and birth defects
It is preventable by avoiding alcohol during pregnancy
Fetal Alcohol Syndrome One child with FAS
costs about $800,000 in health care costs over their lifetime
It is found in all racial and economic groups
The effects are not reversible and do not go away with time
Effects of Smoking Smoking during
pregnancy can also affect the baby
Babies born to women who smoke are usually small at birth (under 5 ½ pounds)
Preterm delivery is also common
Possible low IQ
Effects of Medications Medications you
take can also be harmful during pregnancy
The most devastating ones include Accutane and anti-seizure medications
Ask your doctor about medications you are taking
Pregnancy Exposure ProgramFullerton Genetics Center
Effects of Good Prenatal Care
Good prenatal care is the first step to ensuring a healthy baby
This includes eating healthy, exercising, getting enough sleep, and seeing your doctor
However, there is never any guarantee
Types of genetic diseases
Multifactorial disorders Chromosomal disorders Single gene disorders Mitochondrial disorders
Multifactorial Disorders No clear inheritance pattern
Recurrence risk difficult to estimate
Combination of genetic and environmental factors
The Neural Tube
Neural Tube Defects If the neural tube doesn’t zipper on the
back, the baby will have spina bifida
If the tube is open at the head, the baby will have anencephaly
Spina Bifida Occurs in 1 out of every 1,000 births One of the most common birth defects Cost to society is about $532,000 for
each child with spina bifida Surgery is done immediately following
birth to close the opening Some surgery is also being done while
the baby is still in the womb
Spina Bifida
Spina BifidaThree types: Spina Bifida Occulta
Vertebrae are slightly malformed
Meningocele Opening in the
vertebrae; membranes and fluid protrude
Myelomeningocele Opening in the
vertebrae; membranes, fluid, and spinal cord protrude
Spina Bifida- Who’s at Increased Risk? Women who have previously had a child
with a NTD Women who are insulin-dependent
diabetics Women using some anti-seizure
medications Women with medically diagnosed obesity Women exposed to high temperatures
early in pregnancy It is more common in Caucasian and
Hispanic women
Spina Bifida- How do you prevent it?
Folic acid!! The recommended daily allowance is 400
micrograms But it can be as much as 4000 micrograms
in women at high-risk Folic acid should be taken before
conception through the third month of pregnancy
May reduce your risk by 70% Half of all pregnancies are unplanned
All women of child bearing age should take a vitamin with folic acid!
Anencephaly Occurs when the neural tube doesn’t
close at the back of the skull Without the complete skull, the brain
fails to develop These children are born with a brain
stem, but no brain Most survive only hours or days after
birth
Anencephaly
Anencephaly
Cleft Lip and Palate Occurs in 1 in every 700 births The lip and palate form sometime around 6-12
weeks of pregnancy Surgery is done to close the lip and palate
Children usually do very well with the surgery and develop normal speech
Some studies have shown that folic acid can also be useful in preventing cleft lip and palate
More common in children of Asian descent Has many causes, some of which are genetic
and not preventable
Cleft Lip and Palate
Cleft Lip and Palate
Unilateral Bilateral
Cleft Lip: Before & After
Other multifactorial disorders Asthma
Diabetes
Cardiovascular disease
Cancer
Effects of Genetics Genes also play a role
in how we develop Some birth defects are
due to changes in our genes
These cannot be predicted or prevented
Examples: Down syndrome Some heart defects Sickle cell disease Cystic fibrosis
What is a genetic condition? Any condition caused by a change in a
gene that leads to physical and/or mental differences
May present at birth or later in life
These gene-changes can happen by chance or can be inherited
Background on genetics
Every human being has about 30,000 genes that determine everything from eye color to the development of our physical and biochemical systems.
Genes come in pairs, and we inherit half of our genes from each parent.
Genes are packaged on 46 chromosomes inside our cells
Sperm = 23Egg = 23
Fertilized egg = 46
Typical male 46 XY
Typical female 46 XX
Collecting cells for chromosome analysis
Blood
Tissue
Chorionic villi sampling (CVS)
Amniocentesis
Types of genetic diseases
Multifactorial disorders Chromosomal disorders Single gene disorders Mitochondrial disorders
Chromosome disorders Extra chromosome
Missing chromosome
Rearranged chromosomes
Extra or missing piece of chromosome
Down syndrome 47, +21
Down syndrome Facial features similar to one another Mental retardation Heart problems Intestinal problems Vision and hearing
problems Number of other birth
defects and health problems
Turner syndrome 45, XO
Turner syndrome 45, XO Incidence 1:2500
Major features: Short stature Lack of sexual
development at puberty
Infertility Heart defects Webbed neck
Single Gene Disorders Disorders in which single genes are altered.
Sometimes the altered genes occur pre/post-fertilization, or can be inherited from a parent in the following pattern:
Autosomal recessive Autosomal dominant X-linked
Autosomal recessive Recessive gene on
an autosome Inherit two non-
working copies to be “affected”
Two “carriers” must each pass on the non-working copy. Chance to have an affected child is 25%.
How much of the world’s population is married to their cousin?A. 1 out of 1,000 (0.1%)
B. 1 out of 100 (1%)
C. 1 out of 10 (10%)
D. 1 out of 3 (33%)
First cousins have an increase risk of having a child with a birth defect
http://depts.washington.edu/mednews/vol6/no15/cousins.html
Gives additional
1.7-2.8% risk over general
population
= 6%
Sickle Cell Anemia Incidence 1 in 500
(African Americans) Carrier frequency is 1 in 8
Mutation in B-globin gene on chromosome 11
Features: Joint, stomach, chest or
muscle pain Swelling of abdomen Infections Damage to organs
Cystic fibrosis Incidence 1 in 2500 (Caucasians)
Carrier frequency 1 in 25
CF gene on chromosome 17
Features: Develop thick mucus Sterility in males Abnormal sweat glands Pancreatic insufficiency Life expectancy 30 years in severe cases
Autosomal dominant
Dominant gene on an autosome
Inherit one non-working copy to be “affected”
Parent with genetic condition has a 50% chance of passing to offspring
Marfan syndrome Incidence 1 in
5,000 Due to changes in
the fibrillin 1 precursor (FBR 1) gene on chromosome 15
Major features: Tall, thin stature Heart defect Pectus excavatum Joint laxity
Marfan syndrome – Physical Exam
Hand sign
Arm span
Dislocated lenses
Wrist sign
Heart problems
Marfan syndrome
Famous People with Marfan Syndrome
Flo Hyman – US olympic volleyball player – died of aortic rupture in 1986 at a game in Japan
Abraham Lincoln – suspected diagnosis
Vincent Schiavelli – actor from Ghost,
People vs. Larry Flynt, Tomorrow Never Dies, etc.
Honorary Co-Chair of National Marfan Society
Died in 12/2005 of lung cancer
Neurofibromatosis Incidence 1 in 3000
Mutations in NF1 (17q) and NF2 (22)
Common features: Café au lait patches Neurofibromas Freckling in
groin/armpits
Achondroplasia
Incidence: 1 in 25,000
Mutation in fibroblast growth receptor 3 (FGFR 3) on chromosome 4
Major features: Short limbs Curvature of lower
spine Prominent forehead
Little People, Big World
Little People, Big World
Matt
D A D A
D A D A D A D A
Amy
ZachMolly
JeremyJacob
Diastrophic Dysplasia
Achondroplasia
Famous People with Dwarfism
Jason Acuna Skateboarder, Actor
(Jackass Movies/TV)
Arturo Gil - Actor Charmed, Ally
McBeal, Just Shoot Me, The Man Show
Zach Roloff Little People, Big
World, TLC
Other Autosomal Dominant Conditions
Ehlers Danlos Connective Tissue
Disorder Stretchy Skin Loose Joints – Flexible Risk for Severe Joint
Pain
Osteogenesis Imperfecta (OI) 1 in 10,000 live
births
Most cases of OI are AD and are new mutations
definition: “osteo” = bones “genesis” = creation
of “imperfecta” =
imperfect
Osteogenesis Imperfecta (OI) Mutation in gene that
affects type 1 collagen
There are six types of OI type II is most serious
OI
Treacher-Collins Features include:
malar hypoplasia with downslanting PFs
malformation of external ear
conductive deafness cleft palate small face defect of lower
eyelidSource:www.whick.com
Treacher-Collins Autosomal dominant
60% new mutation
PostoperativePreoperative
Source:www.craniofacialcenter.com
X-linked Recessive Usually affects only
males
Carrier females have a 50% chance of passing on altered X
Duchenne Muscular Dystrophy
Incidence 1 in 3500 males
DMD gene on X chromosome
Features: Progressive muscle
weakness Loss of muscle Death by age 25 years
(cardiac failure)
Mitochondrial Disorders
The mitochondria are organelles outside of the nucleus that are the cell’s batteries
They have their own genetic material
They are inherited only from the mother
Roles of genetic professionals
Clinical geneticist
Genetic counselor
Laboratory geneticist
Important Components of a Genetics Visit
Family History (Pedigree) Age or date of birth (and, for all family members who have passed on,
age at death and cause of death). Medical problems such as:
Cancer Heart disease Diabetes Asthma Mental illness High blood pressure Stroke Kidney disease Alcoholism Birth defects such as spina bifida, cleft lip, heart defects, others. Learning problems, mental retardation. Vision loss/hearing loss at a young age (remember to record the
age it began). Family members with other known medical problems
Medical History
• May be provided through referring physician, collection of medical records, or interviews with the patient or family members
• Often provides important clues pointing to a particular diagnosis
• Identifies the family’s main areas of concerns and specific questions that need to be addressed during the session
• Another important opportunity to complete a psychosocial assessment
Physical Examination
• Helps to establish or rule out a diagnosis
• Based on a standard physical examination
• Incorporates additional elements:
• Dysmorphology examination
• Specific elements may be included dependent upon diagnoses under consideration
Morphology
• (n) The branch of biology that deals with the structure of animals• Basically the study of our pieces & parts and how they fit together
Dysmorphology Altered development The study of malformation syndromes
What does Dysmorphology have to do with Genetics?
Clinical Geneticists use dysmorphology to give them clues as to what genetic syndrome (if any) an individual has
A genetic syndrome is often like a puzzle and the dysmorphic features are like the puzzle pieces
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