General Condition Information
- Tyrosinemia II
- Tyrosinemia type II
- Tyrosinemia type II (tyrosine amniotransferase)
- The prevalence of this rare condition is currently unknown. It is estimated that less than 20 babies are born with this condition in the United States each year.
- The condition may be more common in babies of Middle Eastern and Mediterranean descent.
What is Tyrosinemia, type II
Tyrosinemia type II is an inherited (genetic) condition that prevents the body from processing proteins correctly. Your body breaks down the protein that you eat into amino acids. Your body then uses those amino acids to make other proteins that it needs to function.
There are several enzymes in your body that break down an amino acid called tyrosine. The process of breaking down tyrosine happens in multiple steps. Each step needs a specific enzyme. In tyrosinemia, one of these enzymes is not working well. Either the body does not make enough enzyme, or does not make the enzyme correctly. People with tyrosinemia have trouble with the process of breaking down tyrosine.
In tyrosinemia type II, the nonworking enzyme is tyrosine aminotransferase. As a result, tyrosine and other related substances build up in your baby’s body. This buildup can damage the brain, eyes, and skin. Without treatment, this damage can lead to the signs and symptoms of the condition.
Newborn Screening and Follow-Up
Newborn screening for tyrosinemia type II is done using a small amount of blood collected from your baby’s heel. To learn more about this process, visit the Blood Spot Screening page.
During screening, a special machine measures how much tyrosine is in your baby’s blood. Babies with high levels of tyrosine might have tyrosinemia type II.
If your baby’s blood spot screening result for tyrosinemia type II is out-of-range, your baby’s health care provider will contact you. Together, you will discuss next steps and follow-up plans.
An out-of-range screening result does not mean that your baby definitely has the condition. It does mean that your baby needs more follow-up testing. To learn more about screening results, visit the Blood Spot Screening Results page.
Your baby may need the following tests after an out-of-range screening result:
- Blood and urine tests
- Genetic testing using a blood sample
You should complete any recommended follow-up testing as soon as possible. Babies with this condition can have serious health problems in early childhood if they are not diagnosed and treated quickly.
False-positive newborn screening results for this condition can happen. Babies who are born early (premature) may have out-of-range results. Also, babies with an immature liver, liver disease, or jaundice may have false-positive results.
In some cases, babies have temporary high levels of tyrosine that go away over time. This is called transient tyrosinemia of the newborn. It is a harmless condition and is not a lifelong genetic condition like tyrosinemia type I, II, and III.
Newborn screening helps babies lead healthier lives. If your baby has an out-of-range result, follow up with your health care provider quickly. It is important to follow their instructions. Your baby may need to get treatment right away, even if they are not showing signs or symptoms. In some cases, your baby’s health care provider may decide it is best to watch (monitor) your baby to decide next steps. Careful monitoring and early treatment will help your baby stay as healthy as possible.
Signs of tyrosinemia type II usually begin in the first year of life. These signs may be triggered by eating foods or milk that the body cannot break down or by going long periods without eating. The symptoms can also be caused by illnesses or infections.
Signs of the condition may include the following:
- Increased tear production
- Sensitivity to light (photophobia)
- Eye redness
- Skin lesions on the hands and feet
- Developmental delay
The condition is caused by a change in the TAT gene. This gene gives the body instructions for making the enzyme tyrosine aminotransferase. This enzyme is part of the first step in breaking down the amino acid tyrosine.
Without a working TAT gene, the body cannot break down enough tyrosine. As a result, tyrosine and related substances can build up and cause damage to the body.
- Tyrosinemia type II is an autosomal recessive condition. Babies inherit the condition when each parent passes down a nonworking TAT gene to their baby. Only babies with two nonworking TAT genes—one from the mom and one from the dad—have this condition.
- People with one working copy and one nonworking copy of the TAT gene are called carriers.
- Carriers do not have or develop the condition. However, they may pass down a nonworking copy of the gene to their children.
- If two parents are carriers of a nonworking copy of the TAT gene, they have a 1 in 4 chance of having a child with tyrosinemia type II.
- Carriers for tyrosinemia type II often do not know they are carriers before having a child with the condition. In most cases, families have no history of the condition until the birth of a child with tyrosinemia type II.
- Parents who already have a child with tyrosinemia type II still have a 1 in 4 chance of having another child with tyrosinemia type II. This 1 in 4 chance stays the same for all future children.
- Genetic counselors and medical geneticists can help families learn about this condition and the chance of having children with it. Visit the National Society of Genetic Counselors to find a genetic counselor and the American College of Medical Genetics and Genomics to find a medical geneticist.
Treatment and Management
It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition.
Treatments may include the following:
- Diet low in protein
- Special foods and formulas
Children who receive early and ongoing treatment for tyrosinemia type II can have healthy growth and development.