Uniparental Disomy

Genetic testing for Angelman syndrome, genetic testing for Prader-Willi syndrome

This is a blood test used to see if your child has certain chromosome changes.

Normally, people have 23 pairs of chromosomes in their cells. In each pair, one chromosome comes from their father and one from their mother. These chromosomes contain genes.

Sometimes people will inherit two copies of a chromosome or a part of a chromosome from their mother or father, but none from their other parent. This is called uniparental disomy. In some cases, this causes health problems.

Two health conditions that are often linked to uniparental disomy are Prader-Willi syndrome and Angelman syndrome. This blood test can help find out if a child has uniparental disomy related to one of these syndromes.

Children may have genetic testing to help diagnose them with Prader-Willi or Angelman syndrome. Making the diagnosis of Prader-Willi or Angelman syndrome early in life can help doctors and parents plan for early intervention.

Symptoms of Prader-Willi syndrome often include:

• Difficulty feeding as a baby with poor weight gain. But the child has a very strong appetite as a toddler.
• Obesity
• Undescended testicles and small penis in boys
• Learning and behavior problems
• Delayed puberty and abnormal sexual development

Symptoms of Angelman syndrome often include:

• Small head size
• Developmental problems
• Unusually frequent laughing and smiling
• Notably happy and excitable demeanor
• Frequent flapping hand gestures
• Trouble communicating
• Trouble walking
• Seizures

A child's symptoms help doctors make a diagnosis of Prader-Willi or Angelman syndrome. Your child may need several genetic tests to confirm the diagnosis and figure out if symptoms are caused by uniparental disomy.

Test results may vary depending on your child's age, gender, health history, and other things. Your child's test results may be different depending on the lab used. They may not mean your child has a problem. Ask your doctor what your child's test results mean for them.

The results of gene testing can tell you if your child has one of these disorders. The results can also tell whether uniparental disomy is the cause. The cause of the syndrome may link to how the problem affects your child. For instance, when uniparental disomy is the cause of Angelman syndrome, children are less likely to have a small head, seizures, and certain other problems.

The test is done with a blood sample. A needle is used to draw blood from a vein in your child's arm or hand. A blood sample from your child and both parents may be needed.

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your child's arm or hand, they may feel a slight sting or pain. Afterward, the site may be sore.

No medicines or conditions will affect your child's test results.

Your child doesn't need to get ready for this test.