A urea cycle disorder (UCD) is caused by a defective gene in the body. Genes are part of our DNA, which determines the traits we have, such as eye color or hair color. Everybody has 2 copies of each gene: 1 from their mother and 1 from their father. When a gene isn't working correctly, it can cause health problems. Urea cycle disorders (UCDs) can be caused when one or both parents pass a copy of a defective UCD gene on to their child.
One parent (typically the mother) passes on a defective gene via the X chromosome
· Men who inherit the defective gene will always have symptoms. Women who inherit the defective gene may or may not have symptoms. Men and women who have the defective gene are called "carriers" and can pass it on to their children. OTC deficiency is the only X-linked UCD.
Both parents pass on a copy of a defective gene via any chromosome other than the X or Y chromosomes
· People who inherit two copies of the gene that causes an autosomal recessive UCD will have UCD symptoms
Also called "de novo," a mutation that happened for the first time when the cells were forming, creating a defective gene that caused a UCD
A genetic test or "DNA test" allows doctors to find out if you have any defective genes that may cause a UCD. This test can also tell you your chances of passing a UCD on to your children. A genetic test can be ordered by a primary care doctor, a metabolic geneticist, or a genetic counselor.
During a genetic test, a doctor or nurse takes a sample of your DNA. This is usually done by drawing your blood or swabbing the inside of your mouth.
Then, your sample is sent to a lab where doctors look at your DNA to see if they find the defective gene that causes a UCD.
The results are sent back to your doctor, who will explain whether you have any defective genes related to UCD and what that means for your health.
How much it costs
The cost of a genetic test varies. Health insurance may cover some or all of the cost. You may want to reach out to your insurance company ahead of time to ask if the test will be fully or partially covered. Your doctor or genetic counselor can help you with this.
How long it takes to get the results
It may take several weeks to several months for you to get the results of your genetic test. While you are waiting, it may help to meet with a doctor to discuss symptoms to look out for.
When you can get tested
You can decide to get a genetic test at any time in your life. Your genetic test results do not change over your lifetime.
How the test may affect your job or insurance
Depending on your circumstances, federal law may protect you from discrimination in your job or in getting health insurance based upon genetic test results.
The test is optional
The decision about whether to get a genetic test is a personal one. It may be helpful to talk to a genetic counselor before your genetic test to see if it is right for you.
Who to talk to if you have questions
Genetic counselors are a great source for information about genetic disorders and testing. They can help you understand the testing process and your risk of passing on a UCD.
It is important that you fully understand the following things before you give your permission for genetic testing:
If you have any questions at all or feel unsure about having a genetic test, talk to your doctor or another healthcare professional.
Positive, which means you carry the defective gene or genes that cause a UCD.
Negative, which means the test did not find any defective genes that cause a UCD.
Inconclusive, which means the test found something abnormal but doctors are unsure whether it is the defective gene that causes a UCD. This may require further testing.
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Understand the terms you may hear in your conversations.
Autosomal recessive disorder: A disorder that is caused by a defective gene passed down from both parents to a child.
Chromosome: The part of the cell that carries our DNA. Humans have 22 pairs of chromosomes plus 1 pair of sex chromosomes (an X chromosome and a Y chromosome for males and 2 X chromosomes for females). Chromosomes are found in the nucleus, or control center, of each cell.
Defective gene: A gene that is not working correctly.
DNA: The material that carries all the information about how a person will look and function. DNA determines things such as eye color. Each piece of information is carried on a section of the DNA called a gene.
Gene: A small part of DNA. Genes control how our traits develop, and they pass genetic information on from parent to child.
Genetic counselor: A healthcare professional who helps explain things like the genetics of a disorder, who in a family should have genetic testing, and family planning.
Genetic disorder: An illness caused by a defective gene, which is usually inherited from the parents.
Genetic test: A test in which doctors look closely at someone's genes to determine if he or she has any defective genes that could cause genetic disorders.
Metabolic dietitian: A healthcare professional who educates about nutrition, helps create a plan for a complete and balanced diet, and helps make any dietary changes suggested by a doctor.
Metabolic geneticist: A specialist who treats genetic disorders like UCDs.
Mutation: A change in a gene.
Neuropsychologist: A psychologist who specializes in understanding the relationship between the brain and behavior, as well as how disorders can change behavior and brain function.
Random mutation (also called a "de novo" mutation): An alteration in the DNA caused by a change that happened when DNA was forming.
X-linked disorder: A disorder that is caused by a defective gene passed down from one parent to a child via the X chromosome.