Also known as HCU, homocystinuria is a rare inherited metabolic condition caused by changes in a gene responsible for producing an enzyme called cystathionine beta-synthase (CBS). It is estimated to affect around 1 in 200,000 to 1 in 300,000 people worldwide, although it is more common in some populations.

But what does that mean?

Our bodies use proteins from the food we eat to grow, repair tissues and stay healthy. Proteins are broken down into smaller building blocks called amino acids. One of these amino acids is called methionine.

Normally, methionine is processed through a series of chemical reactions. One of the key helpers in this process is an enzyme called cystathionine beta-synthase (CBS). You can think of enzymes as tiny tools that help important chemical reactions happen in the body.

CBS helps the body break down a substance called homocysteine. This allows homocysteine to be converted into other substances that the body needs.

In homocystinuria, the body does not produce enough working CBS enzyme. As a result, homocysteine and methionine build up in the blood and urine, while the body is unable to produce enough of other important substances. High levels of homocysteine can damage blood vessels and affect many parts of the body.

Because of this, people with homocystinuria can experience a wide range of symptoms, which may include:

• Vision problems: Severe short-sightedness and movement of the lens inside the eye, which can affect vision.
• Bones and joints: A tall, slender build, curvature of the spine (scoliosis), low bone density (osteoporosis), or differences in the shape of the chest.
• Learning and development: Developmental delays, learning difficulties, or mental health challenges.
• Blood vessels: An increased risk of blood clots, which can lead to serious complications such as a stroke or a clot in the lungs (pulmonary embolism).

The severity of homocystinuria varies from person to person. Some babies are identified through newborn screening before symptoms develop, while others may not be diagnosed until later in childhood or adulthood.

Diagnosis and Management

Homocystinuria is often suspected when blood tests show raised levels of homocysteine and methionine. Diagnosis can be confirmed through genetic testing to identify changes in the CBS gene.

Management aims to lower homocysteine levels and reduce the risk of complications. Treatment may include a low-methionine diet, specialised protein substitutes, vitamin B6 (for people whose condition responds to it), folic acid and vitamin B12 supplements, and a medication called betaine. Regular monitoring by a specialist metabolic team is important to ensure treatment remains effective.

Early diagnosis and lifelong specialist care can help reduce the risk of serious complications and enable many people with homocystinuria to live healthy, active lives.

We have received information from a company with a clinical trial focusing on HCU. At present, we only have one trial listed but will work to obtain further trial information.

Click the button underneath the trial to learn more and to get involved:

We hope this page has been helpful and has provided you with an insight into trial information for HCU. Although clinical trials must gain approvals and follow strict regulations and processes to ensure safety, all clinical trials carry some degree of risk.

If you do have an interest in participating in a clinical trial it is important you gather all information available. You can discuss this with your consultant or the lead investigator of a trial who’ll be happy to provide more information and help you make an informed decision without committing to participating.