Urea cycle disorders (UCDs) are passed down through a family’s genes because people in the same immediate or extended families have some of the same genes. This may include the gene that causes ornithine transcarbamylase deficiency or OTC deficiency. If one person in your family has OTC deficiency, there could be others who are affected as well.
OTC deficiency is the most common type of UCD. It is typically passed from a mother to her child through the X chromosome. Women who pass on the OTC gene are often called “OTC carriers,” and learn this when their child is diagnosed. A mother who is an OTC “carrier” has one unaffected gene and one OTC gene. If you’re a woman with a child who has OTC deficiency, you may be a carrier of OTC deficiency as well.
If your child has OTC deficiency, contact your doctor to receive a genetic test that will determine if you are a “carrier.”
The OTC Family Tree which you can download here can help you see who in your family may be at risk for OTC deficiency. Take a few minutes to fill it out, then review it with your doctor or genetic counselor to see who in your family should be tested for the OTC gene.
OTC carriers can have symptoms.
Symptoms such as migraines, vomiting, and exhaustion may be signs of high levels of ammonia in your blood. Over time, high ammonia levels can lead to brain damage.
Use this interactive OTC Symptom Assessor to review other UCD symptoms and see if they apply to you. If you have symptoms, talk with a specialist and share your completed symptom survey with him or her.
If your child has been diagnosed with OTC deficiency, or if you learned that you are an OTC carrier, other people in your family might also be affected. It’s important to let your family members know and to give them as much information as you can about OTC and UCDs.
Starting this conversation with family members might not be easy or comfortable, but talking openly with your family about your experiences and answering their questions can give them a better understanding of the risk. You can explain what being an OTC carrier can mean to their health and suggest that they may want to get a genetic test as well.
Your family members can even get tested at no cost to them with our UCD Genetic Testing Program. Suggest that they download this Genetic Testing Brochure and discuss it with their doctor.
If you don’t feel comfortable talking to them in person, you can take other approaches. Getting on the phone or writing a letter or email are also good options. You can compose your thoughts and all of the important information and then follow up with a personal conversation later on.
Use our Talking to Your Family guide for talking points and a sample letter to help you get started.
Some OTC carriers experience symptoms for some time before they even know they are carriers or that it is damaging their health.
Even people with mild OTC can experience hyperammonemia (too much ammonia) at any age.
There are things you can do to help keep these symptoms under control. An OTC management plan may help!
Carriers may have less severe OTC, which means they may not experience hyperammonemic crises often or even ever. BUT this doesn’t mean carriers don’t experience high levels of ammonia!
There are also programs available to help people afford a genetic test. The UCD Genetic Testing Program provides access to genetic testing for people suspected of having OTC and their family members at no cost.