For couples aware of genetic disorders through family history or based on carrier testing, PGD testing can be performed to help avoid a pregnancy or child born with the specified genetic condition. In genetic disorders where the gene structure is known, such as Cystic Fibrosis or Tay-Sachs, the actual genes of the embryo are examined for presence of the condition. Other genetic disorders, such as Duchenne Muscular Dystrophy or Hemophilia, only affect males and, therefore, the DNA of the embryo is examined to determine the sex and only the female embryos are transferred.
PGD can currently be used to detect the following single gene disorders (more detail is provided for the top 5):
* Cystic Fibrosis is an inherited disease that affects the respiratory and digestive system. Caused by a defective gene, cystic fibrosis affects the body’s mucus and sweat glands, often causing chronic lung infections. It affects about one in 2500 Caucasians and one in 25 is a carrier of the defective gene. It is the most common fatal hereditary disorder affecting Caucasians in the U.S. and requires both male and female carriers to pass it on to children.
* Sickle Cell Anemia is an inherited disease of the red blood cells which can cause attacks of pain and damage to vital organs and can lead to early death. The disease occurs when a person inherits two sickle cell genes or a combination of one sickle cell gene and any one of several other abnormal hemoglobin genes. In the U.S., most cases of sickle cell disease occur among African-Americans, and Hispanics of Caribbean ancestry. About one in every 400 African-Americans has sickle cell disease. It also affects people of Arabian, Greek, Maltese, Italian, Sardinian, Turkish and Indian ancestry.
* Thalassemia is a group of inherited diseases of the blood, causing red blood cell deficiencies. The most severe form, Alpha Thalassemia, results in fetal or newborn death and affects mainly individuals of Southeast Asia, Chinese and Filipino ancestry. Others with milder forms and varying degrees of anemia appear healthy at birth and then slowly show symptoms of the disease. About 100,000 babies worldwide are born with severe forms of the disease each year, most frequently occurring in people of Italian, Greek, Middle Eastern, Southern Asian and African ancestry.
* Tay Sachs Disease is a fatal inherited disease of the central nervous system where affected babies lack the necessary protein for breaking down certain fatty substances in brain and nerve cells. These substances build up and gradually destroy brain and nerve cells, until the entire central nervous systems shuts down, causing the child to go blind, become paralyzed and die by age 5. Tay Sachs occurs most frequently in descendants of Central and Eastern European Jews. About one out of every 30 American Jews carries the gene. Non-Jewish individuals of French-Canadian ancestry and member of the Cajun population in Louisiana are similarly at risk – about 100 times the rate of occurrence of other ethnic groups.
* Myotonic Dystrophy shows up in people at various stages of life and can cause mild or severe symptoms affecting various types of tissues and organs. It affects about 1 in 8,000 people and includes 4 different types: congenital (appearing at birth and is most severe); juvenile (appearing after birth and in teen years); adult (appears in late 20′s to early 40′s); and late onset (appears later after 40′s and is generally mild).
* Fragile X Syndrome is a hereditary condition which can cause learning problems in both males and females.
* Phenylketonuria (PKU) is a rare, inherited metabolic disease that results in mental retardation and other neurological problems when treatment is not started within the first few weeks of life.
* Gaucher’s Disease is a lipid-storage disorder commonly affecting Jewish people of Eastern European ancestry that causes symptoms ranging from none to severe disability and death.
* Retinoblastoma is an intraocular (eye) cancer of childhood that affects approximately 300 children in the U.S. each year, causing many to lose their affected eye(s).
* Hemophilia A & B are genetic disorders of the blood leading to improper clotting, causing patients to suffer from frequent spontaneous bleeding episodes.
* Fanconi Anemia is an inherited anemia that leads to bone marrow failure and affects males and females of all ethnic groups.
* Alzheimers (APP gene) is an incurable neurological disease in which changes of the nerve cells of the brain result in the death of large numbers of cells, causing serious mental deterioration, dementia and death.
* Retinitis Pigmentosa is a progressive degeneration of the retina that affects night vision and peripheral vision and may lead to blindness.
* Epidermolysis Bullosa, a group of inherited disorders in which massive blistering of the skin develops in response to minor trauma varies in severity from minor blistering to a lethal form in which the constant massive blistering and scarring ultimately lead to death.
* Duchenne’s Muscular Dystrophy, characterized by rapidly progressive muscle weakness of the legs and pelvis and later affecting the whole body, usually appears in males 1 to 6 years old.
* P53 Oncogene Mutation occurs with unusually high frequency in tumor tissue. The gene, called P53, mutates in nearly half of all cancers.
* HLA Genotyping involves the exploration of generic information encoded on white blood cells, searching for potentially fatal blood diseases.
* OTC Deficiency, in its most common form, causes death in affected newborn males because of their inability to properly process nitrogen in food proteins due to a genetic defect of the liver.
* Neurofibromatosis (NF1 & NF2) is a genetic disorder of the nervous system that causes tumors to form on the nerves anywhere in the body at any time.
* Multiple Epiphyseal Dysplasia’s, also called Fairbank’s Disease, is an inherited condition resulting in the formation of abnormal epiphyses or bone ends.
* Achondroplasis, or dwarfism, is an inherited condition that is caused by a lack of growth spurt, particularly in the arms and legs at the time of puberty.
* LCHAD is caused by an enzyme defect in the beta-oxidation cycle, resulting in an inability to break down fatty acids into a useable energy source, ultimately causing low blood sugar levels, poor muscle tone, and problems with the functioning of the heart.
* X-Linked Hydrocephalus, transmitted by females and manifested in males, is a disturbance of formation, flow or absorption of cerebrospinal fluid that leads to an increase in volume occupied by this fluid in the central nervous system.
* ADA Deficiency, while very rare and often lethal, results in improper functioning of the body’s immune system and often causes those afflicted to live in sheltered or enclosed environments.
PGD testing is also used in situations involving chromosomal abnormalities due to advanced maternal age and balanced translocation or rearrangement of chromosomes leading to recurrent miscarriages.
The above list of genetic disorders is constantly expanding, as is the technology for PGD testing. For a complete, up-to-date list, please contact The Center directly at 844-HOPEIVF.