Comment: usually, avoid bold in headings. ——Anomalocaris (talk) 10:46, 24 December 2020 (UTC)

Tyrosinemia Type II

Tyrosinemia type II (Oculocutaneous tyrosinemia, Richner-Hanhart syndrome) is an autosomal recessive condition with onset between ages 2 and 4 years, when painful circumscribed calluses develop on the pressure points of the palm of the hand and sole of the foot.

Pathophysiology

Type II tyrosinemia is caused by a deficiency of the enzyme tyrosine aminotransferase, encoded by the gene TAT. Tyrosine aminotransferase is the first in a series of five enzymes that converts tyrosine to smaller molecules, which are excreted by the kidneys or used in reactions that produce energy. This form of the disorder can affect the eyes, skin, and mental development. Symptoms often begin in early childhood and include excessive tearing, abnormal sensitivity to light (photophobia), eye pain and redness, and painful skin lesions on the palms and soles. About half of individuals with type II tyrosinemia are also mentally challenged. Type II tyrosinemia occurs in fewer than 1 in 250,000 individuals.

Symptoms

The Human Phenotype Ontology (HPO) provides the following list of features that have been reported in people with this condition. Much of the information in the HPO comes from Orphanet, a European rare disease database. If available, the list includes a rough estimate of how common a feature is (its frequency). Frequencies are based on a specific study and may not be representative of all studies. You can use the MedlinePlus Medical Dictionary for definitions of the terms below.

Signs and symptoms

4-Hydroxyphenylpyruvic aciduria
Abnormality of the skin
Autosomal recessive inheritance
Growth delay
Herpetiform corneal ulceration
Hypertyrosinemia
Intellectual disability

Diagnosis

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing resources

The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

Newborn screening

An ACTion (ACT) sheet is available for this condition that describes the short-term actions a health professional should follow when an infant has a positive result. ACT sheets were developed by experts in collaboration with the American College of Medical Genetics.
An Algorithm flowchart is available for this condition for determining the final diagnosis in an infant with a positive newborn screening result. Algorithms are developed by experts in collaboration with the American College of Medical Genetics.
Baby's First Test is the nation's newborn screening education center for families and providers. This site provides information and resources about at the local, state, and national levels and serves as the Clearinghouse for newborn screening information.
National Newborn Screening and Global Resource Center (NNSGRC) provides information and resources in the area of newborn screening and genetics to benefit health professionals, the public health community, consumers and government officials.

Treatment

The management of tyrosinemia type 2 revolves around dietary restriction of phenylalanine and tyrosine. This controlled diet typically lowers the blood levels of tyrosine, resulting in rapid resolution of the skin and eye symptoms. However, the effects of this controlled diet on involvement (mental development) remains unclear. In some cases, skin lesions may be treated with oral retinoids.[2]

Last updated: 7/25/2012

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Living with

Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Genetics resources

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by GeneTests, the American College of Medical Genetics, and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference

References

Tyrosinemia. Genetics Home Reference (GHR). 2008; http://ghr.nlm.nih.gov/condition=tyrosinemia. Accessed 2/3/2010.
Wendel U. Tyrosinemia type 2. Orphanet. November 2010; http://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=28378. Accessed 7/25/2012.

Category:Amino acid metabolism disorders Category:Autosomal recessive disorders Category:Palmoplantar keratodermas

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