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HCU Introduction


The Expanded Newborn Screening project has now ended.  As a result of this project screening for this disorder will continue at the pilot sites, and will start at all other sites in England from early 2015.  The information provided in these pages is no longer being actively maintained, and all the information leaflets and technical resources have been superseded by those produced by the NHS Newborn Blood Spot Screening Programme.

Please use the following pages (film and leaflets, resources and fact file) to find out more information about HCU.

What does HCU stand for?

HCU stands for Homocystinuria (HCU) pronounced as ho-mo-sistin-ur-ee-a.

What is HCU?

HCU is a rare disorder that prevents the breakdown of a building block of protein, the amino acid, homocysteine. This then builds up in the blood. In the long term, this can lead to a number of health problems.

What is homocysteine?

Homocysteine is an amino acid. Amino acids are the building blocks from which protein is made. Homocysteine is formed during the  breakdown of protein. Normally, homocysteine is immediately broken down further. People with HCU cannot break down homocysteine, so it builds up in their blood.

What are the effects of having HCU?

Without treatment, most children with HCU have learning difficulties and eye problems. They may also develop bones that are abnormally long and thin (osteoporosis), and blood clots or strokes.  

How is HCU treated?

Treatment is given to prevent the build up of homocysteine. In some children with HCU, the level of homocysteine can be controlled by giving Vitamin B6 (Pyridoxine). These children are called pyridoxine responsive. If vitamin B6 does not work, the children are treated with a special low-protein diet and extra supplements and medicines.


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