Homocystinuria is disorder of the metabolism. It causes low levels of a specific enzyme. These enzymes normally help to break down the amino acids methionine and homocysteine. The build up of these amino acids can cause impaired growth, development, and tissue repair.
The most common form of homocystinuria, involves a deficiency of the enzyme cystathionine beta-synthase.
Homocystinuria is a genetic disorder. The faulty genes are inherited from the parents. Both parents must have the defective gene in order for the child to develop the condition.
Homocystinuria is more common in New South Wales, Australia, and Ireland.
If both parents carry the faulty gene, there is a:
The number and severity of symptoms vary. They may include:
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Early treatment is important. Many states require that newborns be screened for homocystinuria. The test usually looks for high levels of methionine. If the test is positive, blood or urine tests can be done to confirm the diagnosis. These tests can detect high levels of methionine, homocysteine, and other sulfur-containing amino acids. Tests to detect an enzyme deficiency may be done as well.
Prenatal diagnosis of homocystinuria is available. It is done with samples taken during an amniocentesis or chorionic villi sample.
Newborn infants appear normal. Early symptoms, if present, are vague. They may first appear as mildly delayed development or failure to thrive. Increasing visual problems, dislocated lenses and nearsightedness in children may lead to diagnosis. Your doctor may order blood tests to confirm the diagnosis.
To look for potential complications the following tests may also be done:
There is no specific cure for homocystinuria. Treatment is focused on managing the levels of methionine. It should begin as early as possible. Treatment may include medication and/or a special diet.
Those that do not respond to these vitamin will need a combination of a low methionine diet with cysteine supplementation. Other medications may also be occasionally needed.
A special diet may help people who don't respond to or don't respond fully to vitamin B6 treatment. Starting the diet early in life can help prevent intellectual disability and other complications. In general, the diet:
March of Dimes
National Organization for Rare Disorders, Inc.
US National Library of Medicine
Canada Health Portal
Service Canada: Services for Families and Children
Homocystinuria. EBSCO DynaMed website. Available at: https://dynamed.ebscohost.com/about/about-us . Updated August 28, 2011. Accessed December 28, 2012.
Homocystinuria. National Organization for Rare Disorders, Inc. website. Available at: http://www.rarediseases.org/rare-disease-information/rare-diseases/byID/463/viewAbstract . Accessed December 28, 2012.
Last reviewed November 2012 by Michael Woods, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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