Tyrosinemia Type II

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I know that intellectual disability can be associated with Tyrosinemia Type II. Is there a way to predict or prevent whether or not my child will be intellectually disabled?

It is not understood why some people with Tyrosinemia Type II have an intellectual disability and some of them do not. There is no way to predict whether someone with Tyrosinemia Type II will have an intellectual disability nor is there a way to prevent it. However, it is suggested that early treatment can reduce the risk. It is important for the individual with Tyrosinemia Type II to be started on treatment as soon as possible.

References
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-ii
  • Pediatr Int. 2016 Jun 10. doi: 10.1111/ped.13062. [Epub ahead of print]Tyrosinemia type II: novel mutations in the TAT gene in a boy with unusual presentation.Gokay S1, Kendirci M1, Soylu Ustkoyuncu P1, Kardas F1, Kacar Bayram A2, Per H2, Poyrazo?lu HG3
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How many people with Tyrosinemia Type II have an intellectual disability?

My doctor prescribed me something called nitisinone. What is this and what does it do for my Tyrosinemia Type II?

Are symptoms of Tyrosinemia Type II reversible?

Corneal crystals are a side effect of nitisinone. How do I know if I have these if I have Tyrosinemia Type II?

My doctor prescribes me a specialized formula/medical food to take in addition to my nitisinone for Tyrosinemia Type II. What is this and why do I need to take it?

What are good resources for me to learn more or for me to provide to others to learn more about Tyrosinemia Type II?

Is a positive newborn screen the same as a diagnosis for Tyrosinemia Type II ?

There are three different types of Tyrosinemia. How is Type II different from Type I and Type III?

What are other names for nitisinone that is used for Tyrosinemia Type II?

How does nitisinone work?

Is there someone that can provide me with more information and help me with low-protein diet for Tyrosinemia Type II?

What does protein in my diet have to do with Tyrosinemia Type II?

What should I do if I do not have access to a Tyrosinemia Type II specialist?

What are the risks associated with taking nitisinone for Tyrosinemia Type II?

Is there someone that I can talk to in order to understand more about Tyrosinemia Type II?

Do carriers have symptoms of Tyrosinemia Type II?

What data exists on the effects of Tyrosinemia Type II on the baby during pregnancy?

If I am pregnant with Tyrosinemia Type II, should I continue taking nitisinone?

Are there any patient registries for Tyrosinemia Type II?

How many people with Tyrosinemia Type II have an intellectual disability?

Approximately 50% of people who have Tyrosinemia Type II have an intellectual disability.

References
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-ii
  • Pediatr Int. 2016 Jun 10. doi: 10.1111/ped.13062. [Epub ahead of print]Tyrosinemia type II: novel mutations in the TAT gene in a boy with unusual presentation.Gokay S1, Kendirci M1, Soylu Ustkoyuncu P1, Kardas F1, Kacar Bayram A2, Per H2, Poyrazo?lu HG3
My doctor prescribed me something called nitisinone. What is this and what does it do for my Tyrosinemia Type II?

Nitisinone is a drug that stops the breakdown of tyrosine in the body at the second step. If a person is taking this and is on a low-protein diet, it prevents tyrosine and its toxic metabolites from building up in the body.

References
  • Lisa Sniderman King, MSc, CGC, Cristine Trahms, MS, RD, and C Ronald Scott, MD Scott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6.
  • Pediatr Int. 2016 Jun 10. doi: 10.1111/ped.13062. [Epub ahead of print]Tyrosinemia type II: novel mutations in the TAT gene in a boy with unusual presentation.Gokay S1, Kendirci M1, Soylu Ustkoyuncu P1, Kardas F1, Kacar Bayram A2, Per H2, Poyrazo?lu HG3
Are symptoms of Tyrosinemia Type II reversible?

Symptoms that people develop when they are not on treatment can be reversed by starting a low-protein diet and taking nitisinone.

References
  • https://rarediseases.info.nih.gov/gard/3105/tyrosinemia-type-2/resources/8
  • Scott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6. Back to cited text no. 5
  • Pediatr Int. 2016 Jun 10. doi: 10.1111/ped.13062. [Epub ahead of print]Tyrosinemia type II: novel mutations in the TAT gene in a boy with unusual presentation.Gokay S1, Kendirci M1, Soylu Ustkoyuncu P1, Kardas F1, Kacar Bayram A2, Per H2, Poyrazo?lu HG3
Corneal crystals are a side effect of nitisinone. How do I know if I have these if I have Tyrosinemia Type II?

Corneal crystals are also a symptom of Tyrosinemia Type II. If you are on treatment and you are experiencing eyes that are painful and sensitive to light, you may have corneal crystals. Corneal crystals happen when there are high levels of tyrosine in the body. This tyrosine gets deposited in the eye. This can happen when people are treated with nitisinone and have too much protein in their diet.

References
  • Lisa Sniderman King, MSc, CGC, Cristine Trahms, MS, RD, and C Ronald Scott, MDScott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6.
  • http://www.ncbi.nlm.nih.gov/books/NBK1515/
My doctor prescribes me a specialized formula/medical food to take in addition to my nitisinone for Tyrosinemia Type II. What is this and why do I need to take it?

The specialized formula/medical food that your doctor prescribes is an amino acid mixture. For Tyrosinemia Type II, this amino acid mixture does not have phenylalanine or tyrosine. People with Tyrosinemia are treated with a low-protein (low phenylalanine and low tyrosine) diet. This formula helps supplement other amino acids that the person may not be receiving when on this diet. Taking a medical formula ensures that the person with Tyrosinemia Type II is receiving all of the nutrients they need while on a low-protein diet.

References
  • Lisa Sniderman King, MSc, CGC, Cristine Trahms, MS, RD, and C Ronald Scott, MDScott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6.
  • http://www.ncbi.nlm.nih.gov/books/NBK1515/
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-ii
What are good resources for me to learn more or for me to provide to others to learn more about Tyrosinemia Type II?

Resources that explain Tyrosinemia Type II include:

References
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-ii
  • https://rarediseases.info.nih.gov/gard/3105/tyrosinemia-type-2/resources/1
  • Scott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6
Is a positive newborn screen the same as a diagnosis for Tyrosinemia Type II ?

Newborn screening identifies babies who are at risk for having certain disorders. This screen looks at markers that are an indication of a disease, but a positive screening result can also happen because the sample was too small or was taken too early. If newborn screening suggests Tyrosinemia Type II, additional tests will be ordered to definitively diagnose your baby.

References
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-ii
  • Scott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6
There are three different types of Tyrosinemia. How is Type II different from Type I and Type III?

Each type of Tyrosinemia is caused by a deficiency in different enzymes that are part of the pathway to breakdown tyrosine in the body. Tyrosinemia Type I is caused by a deficiency of fumaryacetoacetate hydrolase (FAH), and it is the most common and most severe type of Tyrosinemia.

Tyrosinemia Type II is caused by a deficiency of the enzyme tyrosine aminotransferase (TAT). This type of Tyrosinemia is the second most common. This type of Tyrosinemia does not affect the liver. Instead, symptoms affect the eyes, the skin, and development of the central nervous system.

Tyrosinemia Type III is caused by a deficiency of the enzyme 4-hydroxyphenylpyruvate dioxygenase. Less than 20 people have been documented to have this type of Tyrosinemia. These people do not have liver involvement. Instead, symptoms include poor coordination and balance as well as seizures and intellectual disability.

References
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-i
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-ii
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-iii
  • Scott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6
What are other names for nitisinone that is used for Tyrosinemia Type II?

Other names for nitisinone include:

  • NTBC
  • Orfadin (marketed name by the company that makes nitisinone)
References
  • Lisa Sniderman King, MSc, CGC, Cristine Trahms, MS, RD, and C Ronald Scott, MDScott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6
  • http://www.ncbi.nlm.nih.gov/books/NBK1515/
How does nitisinone work?

Nitisinone is a drug that blocks an enzyme called parahydroxyphenylpyruvic acid dehydrogenase. This prevents the production of succinylacetone, the toxic compound responsible for the symptoms of Tyrosinemia Type I.

References
  • Lisa Sniderman King, MSc, CGC, Cristine Trahms, MS, RD, and C Ronald Scott, MDScott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6
  • http://www.ncbi.nlm.nih.gov/books/NBK1515/
Is there someone that can provide me with more information and help me with low-protein diet for Tyrosinemia Type II?

A licensed dietician can help you with a low protein diet and make sure that you carry it out correctly. Specifically, dieticians that work in metabolic clinics have experience with specialized diets required by other metabolic disorders in addition to Tyrosinemia Type II.The American College of Medical Genetics has a search page on their web site ]ACMG[/link] where you can search for centers with biochemical geneticists, dieticians, and other professionals to manage the care of a person with Tyrosinemia Type II.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1515/
What does protein in my diet have to do with Tyrosinemia Type II?

The main source for the body’s phenylalanine, an amino acid, comes from protein that we eat. The gene responsible for Tyrosinemia Type II is found in the pathway that breaks down phenylalanine. Therefore, the more protein we eat, the more phenylalanine we have. The more phenylalanine we have, the more tyrosine we have as the phenylalanine gets broken down in the body. Tyrosinemia Type II happens when tyrosine cannot be broken down, and excess levels of tyrosine cause health problems.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1515/
  • Scott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6
What should I do if I do not have access to a Tyrosinemia Type II specialist?

Finding a genetic counselor and/or a medical geneticist near you would be an ideal way to make sure you have the information you need to make sure your Tyrosinemia Type II is managed correctly.

Make sure your primary care physician has the appropriate information on Tyrosinemia Type II in order to ensure that you are receiving the proper medical management. You can search the web site of The American College of Medical Genetics to locate genetic services near your home. ACMG.net

References
  • www.nsgc.org
What are the risks associated with taking nitisinone for Tyrosinemia Type II?

Nitisinone can increase the amount of tyrosine in a person’s body. Increased levels of tyrosine can lead to corneal crystals (deposits of tyrosine into a person’s eye). High levels of tyrosine can also cause skin on the palms and feet to become thickened. These side effects can be reversed when tyrosine levels are lowered.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1515/
  • Scott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6. Back to cited text no. 5
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-ii
Is there someone that I can talk to in order to understand more about Tyrosinemia Type II?

A genetic counselor can provide you with more information about Tyrosinemia Type II. Genetic counselors are healthcare professionals that have specialized training in medical genetics and counseling to provide personalized help to patients on their genetic health. If you are in the United States, you can find a genetic counselor by going to http://nsgc.org/p/cm/ld/fid=164. This page is the “Find a Genetic Counselor” tool on the National Society of Genetic Counselors webpage.

References
  • www.nsgc.org
Do carriers have symptoms of Tyrosinemia Type II?

Carriers (people with only one gene change) do not have symptoms or show signs of Tyrosinemia Type II.

References
  • http://www.babysfirsttest.org/newborn-screening/conditions/tyrosinemia-type-ii
  • Scott CR. The genetic tyrosinemias. Am J Med Genet C Semin Med Genet 2006;142:121-6. Back to cited text no. 5
What data exists on the effects of Tyrosinemia Type II on the baby during pregnancy?

Little data exists on the effects of Tyrosinemia Type II during pregnancy. There have been two scientific papers published that outline two women with Tyrosinemia Type II who had babies. Outcomes were very different in both pregnancies. This suggests that control of tyrosine levels is very important.

References
  • Kassel R, Sprietsma L, Rudnick D. Pregnancy in an NTBC-treated patient with hereditary tyrosinemia type I. Journal Of Pediatric Gastroenterology And Nutrition [serial online]. January 2015;60(1):e5-e7.
  • http://journals.lww.com/jpgn/Fulltext/2015/01000/Pregnancy_in_an_NTBC_Treated_Patient_With.31.aspx
If I am pregnant with Tyrosinemia Type II, should I continue taking nitisinone?

You should continue to take nitisinone during pregnancy. The risk of Tyrosinemia Type II on the development of the baby is not well understood. However, the risks associated with nitisinone on the development of the baby are not well understood either. Despite this, the risks of Tyrosinemia Type II to the baby and the mother are considered to be greater than the risks of nitisinone. As of January 11, 2016, nitisinone has not been shown to cause birth defects.

References
  • Kassel R, Sprietsma L, Rudnick D. Pregnancy in an NTBC-treated patient with hereditary tyrosinemia type I. Journal Of Pediatric Gastroenterology And Nutrition [serial online]. January 2015;60(1):e5-e7.
  • http://journals.lww.com/jpgn/Fulltext/2015/01000/Pregnancy_in_an_NTBC_Treated_Patient_With.31.aspx
Are there any patient registries for Tyrosinemia Type II?

A patient registry for Tyrosinemia Type II is Newborn Screen Connect (NBS-Tyrosinemia Connect): https://nbs.patientcrossroads.org/.

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