Conditions Tyrosinemia, Type I

Tyrosinemia, type I (TYR I) is an inherited condition in which the body is unable to break down certain building blocks of proteins, known as amino acids. TYR I is considered an amino acid condition because people with this condition are unable to break down the amino acid tyrosine. Detecting the condition early and beginning treatment can often prevent the severe outcomes of TYR I.

Tyrosinemia is a condition with multiple forms, which each have different outcomes and treatments. TYR I is only one form of the condition. Click on these links to read about different forms of the condition: tyrosinemia type II or tyrosinemia type III.

Condition Type

Amino Acid Disorders


Tyrosinemia, type I (TYR I) affects 1 in 100,000 worldwide. However, TYR I is more common in people of French-Canadian background. The condition affects 1 in 16,000 individuals in Quebec and 1 in 1,846 individuals in the Saguenay-Lac St. Jean region of Quebec.

Also known as

  • TYR I
  • Hereditary tyrosinemia
  • Hepatorenal tyrosinemia
  • Fumarylacetoacetase deficiency
  • Fumarylacetoacetate hydrolase deficiency
  • FAH deficiency
  • Tyrosinosis
  • Hypertyrosinemia

Follow-Up Testing

Your baby’s doctor may ask you if your baby is showing any of the signs of TYR I (see Early Signs below). If your baby has certain signs, your baby’s doctor may suggest starting immediate treatment.

If your baby’s newborn screening result for tyrosinemia, type I (TYR I) was out of the normal range, your baby’s doctor or the state screening program will contact you to arrange for your baby to have additional testing. It is important to remember that an out-of-range screening result does not necessarily mean that your child has the condition. An out-of-range result may occur because the initial blood sample was too small or the test was performed too early. However, as a few babies do have the condition, it is very important that you go to your follow-up appointment for a confirmatory test. Because the harmful effects of untreated TYR I can occur soon after birth, follow-up testing must be completed as soon as possible to determine whether or not your baby has the condition.

Follow-up testing will involve checking your baby’s urine and blood samples for harmful amounts of acids and toxins. Certain acids and toxins build up in the body when a child has an amino acid condition, so studying the amounts of these substances in your baby’s body can help doctors determine if your baby has a condition. High amounts tyrosine in the blood and an amino acid called succinylacetone in the urine might indicate that your baby has TYR I. Sometimes follow-up testing may also include testing a very small sample of skin.

About Tyrosinemia, Type I

Early Signs

There are three types of tyrosinemia (I, II, and III). Tyrosinemia, type I (TYR I) is the most severe of the three forms. Signs of TYR I usually begin in the first few months of life, though some individuals do not begin showing signs until childhood.

Babies with TYR I may show signs such as:

  • Diarrhea
  • Bloody stool
  • Vomiting
  • Poor weight gain
  • Sleeping longer and more often
  • Tiredness
  • Irritability
  • “Cabbage-like” odor
  • Yellowing skin (known as jaundice)
  • Increased bleeding or bruising
  • Swollen legs or abdomen
  • Developmental delays
  • Trouble breathing

Many of these signs may occur when your baby eats foods that their body cannot break down. They can be triggered by long periods of time without eating, illnesses, and infections.

If your baby shows any of these signs, be sure to contact your baby’s doctor immediately.


Dietary Treatments

Your baby may need to be on a restricted diet to avoid proteins that their body cannot break down. A dietician or nutritionist can help you plan the appropriate diet for your child

Your baby’s doctor might also recommend special formulas and foods for children with tyrosinemia, type I (TYR I). These formulas will likely need to be continued through adulthood.

Supplements and Medications

Your doctor may prescribe a medication called nitisinone (also called Orfadin or NTBC). This medication helps stop TYR I from affecting the brain, liver, and kidneys. It is important to screen for TYR I at birth because taking this medication early can prevent liver, kidney, and brain damage.

If TYR I is affecting your baby’s bones, your doctor might also prescribe vitamin D supplements. Vitamin D is a natural substance that can help strengthen bones.

Expected Outcomes

Early treatment can prevent many of the liver, kidney, and brain effects of tyrosinemia, type I (TYR I). Children who receive treatment can have healthy growth and development.

If treatment is not started soon after birth, children risk some liver and kidney damage.

Without treatment, children are at risk for life-threatening kidney and liver problems.


When we eat food, enzymes help break it down. Some enzymes help break down proteins into their building blocks, called amino acids. Other enzymes break down these amino acids. In tyrosinemia, type I (TYR I), the enzyme fumarylacetoacetate hydrolase (FAH) is not working correctly.

FAH’s job is to break down the amino acid tyrosine. Babies with TYR I do not make enough FAH. When there is a shortage in FAH, the body cannot break down tyrosine. Tyrosine builds up in the body, which can be toxic.

TYR I is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for TYR I, one from each parent, in order to have the condition. The parents of a child with an autosomal recessive condition each carry one copy of the non-working gene, but they typically do not show signs and symptoms of the condition. While having a child with TYR I is rare, when both parents are carriers, they can have more than one child with the condition. Learn more about autosomal recessive inheritance.

Support for Tyrosinemia, Type I

Support Services

Support groups can help connect families who have a child or other family member affected with tyrosinemia, type I with a supportive community of people who have experience and expertise in living with the condition. These organizations offer resources for families, affected individuals, health care providers, and advocates:

Accessing Care

Work with your baby’s doctor to determine the next steps for your baby’s care. Your baby’s doctor may help you coordinate care with a doctor who specializes in metabolism, a dietician who can help plan your child’s specialized diet, and other medical resources in your community. Depending on the signs and symptoms your baby experiences, your baby’s doctor may work with other doctors who specialize in treating the liver or kidneys. Some children with tyrosinemia, type I (TYR I) have developmental delays. If you think that your baby is not meeting their developmental milestones, ask your baby’s doctor about the next steps in accessing a developmental evaluation and care.

Because TYR I is a genetic condition, you may want to talk with a genetics specialist. A genetic counselor or geneticist can help you understand the causes of the condition, discuss genetic testing for TYR I, and understand what this diagnosis means for other family members and future pregnancies. Speak with your baby’s doctor about getting a referral. The Clinic Services Search Engine offered by the American College of Medical Genetics and Genomics (ACMG) and the Find a Genetic Counselor tool on the National Society of Genetic Counselors (NSGC) website are two good resources for you or your baby's health care provider to use to identify local specialists.

Families' Experiences

Joshua was diagnosed with tyrosinemia when he was one-year-old. While he experienced numerous health challenges in his first year of life because the condition was not detected early, his health quickly improved as a result of his diagnosis and beginning a new diet and treatment. His story shows the importance of early identification of the condition. Duke Children’s Hospital created a video in honor of Joshua.

Kyle was diagnosed with tyrosinemia when he was one-year-old. Because the condition was not identified early, he has experienced a number of health challenges. Kyle managed to stay cheerful through two liver transplants, and now, years later, he is much healthier. Read his story on the Cincinnati Children’s Hospital Medical Center website.

References & Sources

Visit the Screening, Technology And Research in Genetics Project (STAR-G) for more information on tyrosinemia, type 1

Visit MedlinePlus Genetics for more condition information

Read this fact sheet prepared by the Illinois Department of Public Health for more information

ACT Sheets

Healthcare professionals can learn more about confirmatory testing by reading the American College of Medical Genetics and Genomics' Algorithm for Diagnosis and ACT Sheet, a guide for follow-up after newborn screening. You can visit this page of the ACMG website here.

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