Genetics2

 

 Comparitive Table of Birth Disorder Risks
In order of frequency

*Glossary of inherited genetic disorders terms:
 

Disorders
with description of related problems:		 Cause: Mostly Affects:  Risk: Screen/Treat
Low Birth Weight, Stillbirth, SIDS
(Related problems for survivors include brain damage, breathing problems, anemia, heart conditions)		 Multi-factoral
 

 

 Random
 
 
 

 

 Background risk: 
one out of every 15 births

First Cousins: Consanguinity unlikely to cause an increase in risk

 Most Common Causes:
  • Maternal medical health and nutrition  
  • Smoking  
  • Drinking 
    Drug Use (Rx, OTC and illegal)
Congenital Heart Defects *

* Usually NOT genetic

 Multi-factoral
common causes: environmental, viral, medicinal, alcholol and other substance use during pregnancy		 Random
 
 

 

 Background risk: 
one out of every 150 births

First Cousins: Consanguinity unlikely to cause an increase in risk

 Screening: 
Echo- Cardiography

Treatment:
Pre- and Post-Natal treatments available

 

Cerebral Palsy
May have other problems such as mental retardation; learning disabilities; seizures; and vision, hearing and speech problems		 Multi-factoral
 
 

 

 Random
 
 

 

 Background risk: 
one out of every 350-500 births

First Cousins:
Consanguinity unlikely to cause an increase in risk

 Common Causes:
Infection during pregnancy, Premature birth, delivery trauma, Rh disease

 

Sickle Cell
Affects a protein inside the red blood cells called hemoglobin causing distorded cells. Pain, meningitis, stroke, and organ problems are associated with this disease.		 Recessive Genetic

Gene must be present in BOTH parents for child to be affected:
 

 African-American, also Hispanic, Caribbean and certain other ethnic groups
 
 

 

 Background risk:
one out of every 400-600 births

First cousins: 
may increase risk up to 2x (2 out of every 400-600 births)

 Screening: Prenatal testing availale; Newborn testing is standard in 40 states.

Treatment: infants should be treated with pennicillin to pevent fatality
 

Club Foot *
Mild to severe foot deformities
 

 

 Multi-factoral
Usually a result of fetal positioning, although in rare incidents, can be dominant genetic.

Rarely inherited!

 Random
affects males 2x more often than females

 

 Background Risk:
one out of every 735 births

First Cousins:
Consanguinity unlikely to cause an increase in risk

 Treatment: Affects can be minimized by early treatment, i.e. casting, braces, or surgery
FAS 
(Fetal Alcohol Syndrome)
miscarriage, stillbirth, SIDS, low birthrate, mental retardation or learning disabilities, heart and other organ problems

 

 Alcohol Consumption
 
 
 
 

 

 Random
entirely preventable
 
 
 
 

 

 Background risk:
one out of every 750 births

First Cousins:
Consanguinity does not affect risk

 Treatment: Varies

Because no amount of alcohol is proven safe, women should stop drinking immediately if they suspect that they might be pregnant. This refers to all types of alcohol, including wine, wine coolers, beer and mixed drinks.

Cleft Lip and Palate Failure of the cleft and/or the palate to close during during pregnancy causing facial disfiguration
 
 
 

 

 Combination of genetic elements and environmental factors, such as drugs, infections, maternal illnesses, and possibly deficiency of folic acid Random, but mostly affecting Asians, American-Indians Background risk:
one out of every 930 births

First Cousins: Consanguinity unlikely to cause an increase in risk

Risk is increased by mothers who smoke, abuse alchohol, or have diabetes.

 Treatment:  Surgery
Toxoplasmosis
(causes stillbirth, hearing loss, hydrocephalus, mental retardation, learning disabilities, vision impairment or seizures) 

Can cause Cerebral Palsy

 Parasitic Infection
(usually contracted from exposure to cat feces or eating undercooked meat)

fetuses contract it from mothers
 

 Random
60 to 85% of American women of childbearing age have never had toxoplasmosis and are susceptible to it during pregnancy		 Background risk:
one out of every 1000 births 

First Cousins: Consanguinity does not affect risk

 Screening: Maternal blood tests, amniocentesis

Treatment: Post-natal antibiotics

Fragile X Syndrome
(intellectual disorders, ranging from mild learning disabilities to mental retardation)		 X-linked Random
Affects males, although women can be carriers		 Background risk: 
1 of every 1000 males 
1 of every 700 females born are carriers

First Cousins: Consanguinity unlikely to cause an increase in risk

 Screening: 
Molecular DNA test
Rh Disease
 It is a hemolytic disease that causes destruction of fetal red blood cells. Can result in jaundice, anemia, brain damage, heart failure and death. It does not affect the mother’s health.		 Incompatibility between the blood of a mother and her fetus. 

Rarely affects first-born children

 Random, but affects caucasions 2x more often than African-Americans.

 

 Background risk: 
one out of every 1,400 births

First Cousins: 
Consanguinity unlikely to cause an increase in risk

 Screening: amniocentesis, experimental tests

Treatment: 
Rhlg injections during pregnancy and postpartum; possible blood transfusion.

Down’s Syndrome
Dwarfism, abnormal bone structure, learning disabilities, mental retardation, short life span

 

 Chromosomal
 
 
 
 

 

 Random 
 
 
 
 

 

 Mothers Age:
20: 1:10,000
35: 1:333
40: 1:100

First Cousins: Consanguinity unlikely to cause an increase in risk

 Screening: Amniocentesis or CVS
 
 
 
 

 

Spina Bifida
failure of the fetus’ spine to close properly during pregnancy		 Combination genetic and environmental

only 5% of all spinal bifida disorders occur in families with previous history.
 

 Hispanics, Whites of European descent
and occasionally other ethnic groups		 Background risk:
one out of every 2000 births 
recurrance rate: 1:40

First Cousins:
risk may be increased by 1.5% (1 of 1500 births)

 Screening: Prenatal Ultrasound or AFP 

Treatment: folic acid during pregnancy

Cystic Fibrosis
Excess production of unusually thick mucous, collecting in lungs. Can cause damage to pancreas. Shortened life-span.
 		 Recessive Genetic, hereditary
 

 

 Mostly Caucasion
 

 

 Background risk 
one out of every 2500 births

First Cousins:
risk may double (2 out of every 2500 births)

 Screening:
Amniocentesis or CVS  90% accurate

 

Neurofibromatoses
The movie "Elephant Man" was about someone who had NF1
(also known as von Recklinghouasen’s disease {NF1}
and vestibular schwannoma {NF2})		 Dominant Genetic or Spontaneous gene mutation Random
 

 

 Background risk: (NF1)
1 of every 4,000 births

Background risk: (NF2)
1 of every 40,000 births

First Cousins: Consanguinity unlikely to cause an increase in risk

 Treatment: 
Medical proceedures can help minimize the problems associated wih NF
Hemophilia 
("The Royal Family disease") Inability for blood to clot properly
 
 

 

 X-linked
 
 
 
 

 

 Random
 
 
 
 

 

 Background risk:
1 of every 10,000 males (Men are rarely carriers as this is an X-linked disorder. Females rarely have the disorder, and if so the symptoms are much less severe)

First Cousins: Consanguinity does’t increase the risk of hemophilia since only the mother is a carrier; the father is irrelevant.

 Screening:
Genetic tests are available for parents and fetuses

Treatment: Concentrated clotting factors can be administered at home.

 

Marfan Syndrome
variable pattern of abnormalities that may affect the heart, blood vessels, lungs, eyes, bones and ligaments		 Dominant Genetic / Chromosomal Random Background risk:
1 of every 10,000 births

First Cousins: Consanguinity unlikely to cause an increase in risk

 Screening:
None available
PKU (phenylketonuria)
Affects the way the body processes protein.
Causes mental retardation if left untreated

 

 Recessive Genetic
 
 

 

 Random, 
but with highest occurance in Northern Europeans

 

 Background Risk: 1 of every 12,000 births in U.S.

First Cousins: consanguinity may increase risk by double (2 of every 12,000 births in U.S.)

 Screening: 
Standard post-natal

Treatment:
Special diet low in phenylalanine, Nitric Oxide Therapy

Achondroplasia
Abnormal bone growth, (affecting height)		 Chromosomal,
occasionally
Dominant Genetic

Only 20% of cases are inherited

 Random
 
 
 

 

 Background risk:
1 of every 26,000 births

Highest risk: fathers over age 50

First Cousins: Consanguinity highly unlikely to cause an increase in risk

 Screening: 
highly accurate prenatal testing available
 
 

 

Muscular Dystrophy
Affects the central nervous system. Rarely diagnosed before age 12
 
 
 
 

 

 Genetic, usually hereditary

various forms include dominant genetic, recessive genetic, and x-linked.
 

 

 Random
Severe types affect boys almost exclusively
 
 
 

 

 Background Risk: Affects more than 300,000 people in the U.S., and 2,500,000 people worldwide

First Cousins: Consanguinity unlikely to cause an increase in risk in dominant and x-linked forms, may increase risk in recessive forms of the disease.

 Screening:
protein and DNA testing can rule out certain types of MS
 
 
 
 

 

Tay Sachs
loss of motor skills, blindness, inevitable death by age 5
 
 
 
 

 

 Recessive Genetic
 
 
 
 
 
 

 

 Jewish, French-Canadian
 
 
 
 
 
 

 

 No stats on National Average, however: 

30% of all Jews and French-Canadians are carriers. Two carriers have a 1:4 probability of having a child born with TaySachs.

First Cousins: greater probability of both cousins being carriers

 Screening:
Amniocentesis or CVS
 
 
 
 
 
 

 

Thalassemia
Can cause anemia, organ enlargement, and pre- or post-natal death

 

 Recessive Genetic
 
 

 

 Italian, Greek, Middle Eastern, Southern Asian and African ancestry

 

 100,000 infants worldwide

First Cousins:
risk may be as much as 2x background risk.

 Screening:   amniocentesis or CVS

Treatment:
Blood transfusions + antibiotics

 

PKD
Only 50% of affected individuals experience problematic symptoms, including cysts on kidneys and liver, enlarged organs, and occasional Hiatal hernias or brain aneurysms		 Dominant Genetic
 
 

 

 Random
 
 

 

 500,000 cases in US, rarely affecting infants

First Cousins: Consanguinity unlikely to cause an increase in risk

 Screening: Available for pre-natal and adults

Treatment: General physical and nutritional health, in some cases dialysis or kidney transplant is recommended

Other problems which commonly cause birth defects are:

  • Cocain use during pregnancy (affects 45,000 babies each year in the U.S.) can cause stroke, brain damage, prenatal addiction, death
  • STD’s: Syphillis affects 1:2,000 newborns, and 1:2,700 babies are born HIV+ each year. Over 500,000 new cases of Genital Herpes occur each year, including about 1,000 in newborn babies.
  • Medicinal drugs, including Thalidomide, Accutane and other retinoids, and ingredients in many common over the counter medications have been responsible for tens of thousands of birth defects ranging from mild facial distortions, to missing limbs, and even death in recent decades.


This is by no means an all-inclusive list! There are between three and five thousand known birth defects, affecting 150,000 babies each year.  Sixty percent of all birth defects have unknown causes. According to the Centre for Human Genetics, and the NSGC, every couple has approximately a 3% risk of having a child with a birth defect. This risk is additionally increased by 1.5 to 3% for children born to first cousins. Little, if any increased risk exists for more distantly related individuals.

Glossary:

Dominant Genetic: One affected parent has a single faulty gene (D) which dominates its normal counterpart (d). Each child produced has a 50% risk of inheriting the D, and the disorder from the affected parent. If both parents have the faulty gene, each child has a 75% risk of inheriting the disorder.

X-Linked Genetic: Passed on only through the mother. The mother, who has a defective gene on one of her two sex chromosomes, is protected against the defect because her normal sex chromosome (x) compensates for the defect on the other (X). The father has normal male sex chromosomes (x and y). Each male child has a 50% risk of inheriting the faulty X, and the disorder, and a 50% chance of inheriting the normal x chromosome. Each female child has a 50% risk of inheriting the faulty X and becoming a carrier like her mother, and a 50% chance of inheriting two normal X chromosomes.

Recessive Genetic: Both parents, usually unaffected, carry a defective gene (g) but are protected by the presence of a normal gene (G) which is generally sufficient for normal function. Each child produced has a 25% risk of inheriting a double dose of the g gene, which may cause a serious genetic defect; a 25% chance of inheriting two normal genes; and a 50% chance of being a carrier like both parents.

Sources:
March Of Dimes,
Imaginis Women’s Health Network,
Yale-New Haven Teacher’s Institute,
The Polycystic Kidney Research Foundation

 © 2000 Christie Schuler Smith for CUDDLE International and cousincouples.org