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Genetic Conditions and Birth Defects

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1 Genetic Conditions and Birth Defects
Camila Vieira Shanahan, MS, CGC Genetic Counselor Fullerton Genetics Center February 17, 2012

2 Outline Prenatal Exposures Types of Genetic Conditions Genetics Clinic
Multifactorial disorders Chromosomal disorders Single gene disorders Mitochondrial disorders Genetics Clinic

3 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.

4 With every pregnancy, the chance for a baby to be born with a birth defect is…

5 Pregnancy Timeline

6 Maintaining a healthy lifestyle is important during pregnancy
What do you think having a healthy lifestyle might mean?

7 Which of the following can cause more harm to a fetus?
Cigarettes Crack/Cocaine Heroin Alcohol

8 “Alcohol causes more damage to the developing fetus than any other substance, including marijuana, heroin, and cocaine.” Institute of Medicine, 1996

9 Effects of Alcohol Consumption of alcohol during pregnancy can have devastating effects on the baby No amount of alcohol is okay What kinds of effects do you think alcohol can cause during pregnancy?

10 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

11 Characteristic FAS Facial Features
Source: www. Source:

12 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

13 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


15 Effects of Smoking Smoking during pregnancy can also affect the baby
                                        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 What effects do you think smoking might have on a baby?

16 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 Are medications usually something you would think would be harmful to a baby? What could you do to find out?

17 Pregnancy Exposure Program Fullerton Genetics Center

18 Effects of Good Prenatal Care
                                             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

19 Types of genetic diseases
Multifactorial disorders Chromosomal disorders Single gene disorders Mitochondrial disorders

20 Multifactorial Disorders
No clear inheritance pattern Recurrence risk difficult to estimate Combination of genetic and environmental factors

21 The Neural Tube

22 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

23 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

24 Spina Bifida

25 Spina Bifida Three types: Spina Bifida Occulta Meningocele
Vertebrae are slightly malformed Meningocele Opening in the vertebrae; membranes and fluid protrude Myelomeningocele Opening in the vertebrae; membranes, fluid, and spinal cord protrude

26 Spina Bifida

27 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

28 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! Not all cases of spina bifida are preventable. Some women who take the recommended amount of folic acid still have children with neural tube defects and we believe there is some underlying genetic cause that explains this.

29 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

30 Anencephaly The presence of the brain stem allows these children to breathe and their hearts to beat, but they have no cognitive function.

31 Anencephaly

32 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


34 Cleft Lip and Palate

35 Cleft Lip and Palate Bilateral Unilateral

36 Cleft Lip: Before & After

37 Other multifactorial disorders
Asthma Diabetes Cardiovascular disease Cancer

38 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 Explain some genes and chromosomes, show karyotype

39 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

40 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

41 Sperm = 23 Egg = 23 Fertilized egg = 46


43 Typical male 46 XY

44 Typical female 46 XX

45 Collecting cells for chromosome analysis
Blood Tissue Chorionic villi sampling (CVS) Amniocentesis

46 Types of genetic diseases
Multifactorial disorders Chromosomal disorders Single gene disorders Mitochondrial disorders

47 Chromosome disorders Extra chromosome Missing chromosome
Rearranged chromosomes Extra or missing piece of chromosome

48 Down syndrome , +21

49 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

50 Turner syndrome 45, XO

51 Turner syndrome 45, XO Incidence 1:2500 Major features: Short stature
Lack of sexual development at puberty Infertility Heart defects Webbed neck

52 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

53 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%.

54 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%)

55 Gives additional 1.7-2.8% risk over general population
First cousins have an increase risk of having a child with a birth defect Gives additional % risk over general population = 6%

56 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

57 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

58 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

59 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

60 Marfan syndrome – Physical Exam
Hand sign Arm span Dislocated lenses Wrist sign Heart problems

61 Marfan syndrome

62 Famous People with Marfan Syndrome
Flo Hyman – US olympic volleyball player – died of aortic rupture in 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

63 Neurofibromatosis Incidence 1 in 3000
Mutations in NF1 (17q) and NF2 (22) Common features: Café au lait patches Neurofibromas Freckling in groin/armpits

64 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

65 Little People, Big World

66 Little People, Big World
Achondroplasia Diastrophic Dysplasia Matt Amy D A D A Jacob Jeremy Zach Molly D A D A D A D A

67 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

68 Other Autosomal Dominant Conditions
Ehlers Danlos Connective Tissue Disorder Stretchy Skin Loose Joints – Flexible Risk for Severe Joint Pain

69 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

70 Osteogenesis Imperfecta (OI)
Mutation in gene that affects type 1 collagen There are six types of OI type II is most serious

71 OI

72 Treacher-Collins Features include:
malar hypoplasia with downslanting PFs malformation of external ear conductive deafness cleft palate small face defect of lower eyelid

73 Treacher-Collins Autosomal dominant 60% new mutation Preoperative

74 X-linked Recessive Usually affects only males
Carrier females have a 50% chance of passing on altered X

75 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)

76 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

77 Roles of genetic professionals
Clinical geneticist Genetic counselor Laboratory geneticist

78 Important Components of a Genetics Visit

79 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


81 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

82 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

83 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 Discuss the basics of Morphology Webster's defines “Morphology” as the branch of biology that deals with the structure of animals Basically it is a study of our pieces and parts and how they fit together

84 Dysmorphology Altered development The study of malformation syndromes

85 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 Clinical Geneticists try to figure out what may be causing a person’s symptoms They look at the different symptoms and try to see if they fit together to fit into a known Syndrome So, you can think about a person’s dysmorphic features as puzzle pieces We try to fit them together and see if we can create a picture of a known syndrome Why is it good to know what syndrome someone has? There may be other health problems that we are missing It may tell us what treatment would work best

86 Questions?

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