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Medical information you need to know as an adult with homocystinuria

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Overview of the Condition:

Homocystinuria is a rare metabolic condition in which a chemical called CBS does not work correctly in your body. This can cause two chemicals, homocysteine and methionine, to build up in your blood over time. When these build up too much, they can cause serious health problems. You can manage homocystinuria throughout your life with a special low-protein diet, drug therapy with betaine and other medicines, and ongoing health care.

Another name for homocystinuria is CBS Deficiency.

Medical Problems for Babies and Children:

  • Babies with homocystinuria usually have no or few apparent symptoms.
  • Babies and children with homocystinuria who do not get treated for it are at greater risk for serious health problems later in life.
  • Children with this condition may have learning delays, seizures and eye problems.
  • Eye problems can include partial dislocation of the lens, severe nearsightedness, and quivering of the iris.
  • Newborns in the US are now tested for homocystinuria. If the condition is identified early and treatment and diet are followed carefully, many health problems can be prevented or lessened.

Medical Problems for Teens and Young Adults:

  • Teens and young adults with homocystinuria who have been identified young and treated from early on may have few or none of these health complications.
  • Blood clots are a serious health risk for teens and young adults with homocystinuria. You must monitor your blood homocysteine levels to avoid blood clots, which could cause life-threatening blockages to your heart or lungs.
  • Low bone density (osteoporosis) can be a problem for about half of people who have homocystinuria. Some teens or young adults develop scoliosis, a curving of the spine. Osteoporosis often occurs by age 20.
  • Adults with homocystinuria may be at risk for developing serious neurological or mental health problems including depression, anxiety, psychosis, or seizures. Counseling and medication can help. If you have trouble with your mental health, it is important to get in touch with your health care provider to get treatment.

How to Minimize Medical Problems and Complications:

  • Follow a low-protein/low-methionine diet recommended by your dietician.
  • Take betaine and other medicines recommended by your health care providers.
  • Some people with homocystinuria do well taking vitamin B6 (pyridoxine). Your doctor can help you learn if vitamin B6 works for you.
  • If you have poor vision, visit your eye doctor for regular exams.  Be sure to let your eye doctor know you have homocystinuria.
  • Keep your immunizations up-to-date.
  • Stay in regular contact with your health care providers and health specialists.

Fertility and Pregnancy

  • Homocystinuria does not affect your ability to have children.
  • Genetic counseling can help you and your partner understand the risks to your children. Your doctor can refer you to a genetic counselor who has a special understanding of your health issues.
  • Pregnant women with homocystinuria must follow a careful diet with special guidance from a dietician and health care providers.
  • Pregnancy is considered high risk because of the possibility of blood clots, especially after the baby is delivered. Some women may need anti-blood-clotting medicine.
  • Women with homocystinuria should not use birth control pills that contain estrogen, as these increase the risk of blood clots. Talk with your doctor about non-estrogen birth control.

How to Get Support:


AAP/AAFP/ACP Transition Clinical Report

Transition Toolkit (New England Consortium of Metabolic Programs)

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National Institutes of Health – Genetics Home Reference – Homocystinuria

Genetics Referrals:

Clinical Services

Find Genetic Services

What Next?

Now you can fill out the Medical Health Summary, print it, and save it. This will help you keep important medical information in one place.


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This Metabolic Condition Basics guide was adapted with permission from the American College of Medical Genetics ACT Sheet

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