Genetic Conditions We Can Test for with Preimplantation
Genetic Diagnosis (PGD)

One of the greatest benefits of Preimplantation Genetic Diagnosis (PGD) is the fact that parents have the opportunity to eliminate the risk of passing on any hereditary diseases to their children.

PGD is used to test for more than 100 genetic conditions by performing a biopsy on one or two cells extracted from eight or more early embryos.

At Bridge Clinic, we are currently able to test for the following 13 genetic disorders and chromosomal abnormalities:

Galactosemia

This rare genetic metabolic disorder affects an individual’s ability to process the sugar known as galactose properly. There are three different types of galactosemia, with galactosemia type I being the most common and the most severe. Complications of galactosemia include liver damage, premature ovarian insufficiency, speech difficulty and intellectual disability.

Sickle cell anaemia

Sickle cell disease (SCD), as it is also known, is a serious genetic disorder affecting the red blood cells that carry oxygen throughout the body. People who suffer from SCD carry abnormal haemoglobin in their blood, causing the red blood cells to take on the form of a sickle, instead of the usual disc shape. The red cell sickling and poor oxygen delivery cause severe pain known as pain crises. Over time it also results in organ damage, causing harm to a person’s spleen, brain, eyes, lungs, liver, heart, kidneys, penis, joints, bones, or skin.

Cystic fibrosis

People affected by cystic fibrosis have a defective gene that causes a thick build-up of mucus in the lungs, pancreas and other organs. They are prone to lung infections and need to work closely with healthcare professionals to steer clear of germs as much as possible. The build-up of mucus in the pancreas can stop the absorption of food and nutrients, causing malnutrition.

Glycogen storage disease

Glucose is a large energy source for the body, stored in the form of glycogen. It is released into the blood as needed with the help of special proteins called enzymes. When a person has glycogen storage disease, they have genetically defective enzymes that cannot successfully perform the tasks of controlling the change in sugar levels. Symptoms may include poor growth, muscle cramps, low blood sugar, a greatly enlarged liver and a swollen belly.

Polycystic kidney disease

Polycystic kidney disease causes numerous fluid-filled cysts to grow in the kidneys. If too many cysts grow or they become too big, the kidneys can become damaged. Most people don’t develop symptoms until they are 30 or 40 years old and these include back pain, blood in the urine, frequent bladder or kidney infections and high blood pressure.

Familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic disorder characterised by high cholesterol levels, specifically very high levels of low-density lipoprotein, known as ‘bad cholesterol’ in the blood. This can cause cardiovascular disease to manifest at a young age.

Haemophilia

This sex-linked recessive genetic disease is more likely to occur in males than in females and impairs the body’s ability to control blood clotting. While there is a common perception that those suffering from haemophilia can bleed to death from a small cut or scratch, the truth is that most bleeding actually occurs internally, into muscles and joints. It is not always clear what causes bleeding.

Duchenne muscular dystrophy

This rare x-linked disease affects around 1 in 3 600 boys. It causes muscle degeneration, starting in the legs, then progressing to the arms, neck and other areas, mostly ending in premature death.

Turner syndrome

This genetic disease affects females exclusively and is caused by a missing or partially missing X chromosome. Signs and symptoms of the disease vary, but in most cases persons affected will have a short, webbed neck, a low hairline, short stature and swollen hands and feet at birth. Women who suffer from Turner’s syndrome are typically without menstrual cycles, do not develop breasts and are unable to have children.

Klinefelter Syndrome

Klinefelter syndrome is a genetic condition that results from the presence of an extra copy of the X chromosome in males. One of the main effects of the syndrome is stunted testicular growth and low sperm production. It is often not diagnosed until adulthood.

Hypophosphatemic rickets

This disorder is related to low levels of phosphate in the blood. Phosphate is essential to the formation of bones and teeth. The condition is often picked up in early childhood and signs and symptoms vary greatly from one person to the next. In the most severe cases, growth is stunted and bone abnormalities occur. The most noticeable of these abnormalities would be bowlegs or knock-knees.

Apart from these hereditary genetic conditions, we are also able to test for the following chromosomal abnormalities at Bridge Clinic, using a similar method to PGD

Down syndrome

Perhaps the most recognisable chromosomal abnormality, Down syndrome, is caused by the presence of a third copy or partial third copy of chromosome 21. Symptoms and signs of the condition include small stature, an upward slant to the eyes, low muscle tone and mild intellectual disability. It is not hereditary and the extra chromosome occurs by random chance.

Edwards’ syndrome

This condition is caused by the presence of an extra copy of the 18th chromosome, or part thereof. It is considered a very serious condition disrupting a baby’s development in the womb, with many cases ending in miscarriage or stillbirth. Babies who are born with the condition rarely survive longer than one year of age.