Homocystinuria (HCU) is a rare but potentially serious inherited condition.
Normally, the body breaks down protein in food into amino acids. Chemicals in the body called enzymes process the amino acids further.
Someone with HCU cannot properly process the amino acid methionine.
This causes a build-up of methionine and another amino acid called homocysteine. These can cause problems in the eyes, brain, bones and blood vessels if not treated.
Screening for HCU
Babies are screened for HCU as part of heel prick screening. They are offered heel prick screening when they are 3 to 5 days old.
If your baby has HCU
If your baby has HCU, they can get treatment which will reduce the risk of serious complications.
Your baby will be seen in the National Centre for Inherited Metabolic Disorders (NCIMD), Children's Health Ireland at Temple Street. They will be cared for by a specialist metabolic team, including a metabolic doctor, nurse and dietitian.
Symptoms of HCU
HCU does not usually cause symptoms in the first year of life. But without early treatment, severe symptoms can develop later.
These may include:
- vision problems, such as severe short-sightedness
- weak bones (osteoporosis)
- bone and joint problems
- blood clots
- strokes
- brain damage - which can affect development
Treating HCU
Treatment for HCU may include:
- high doses of vitamin B6 (pyridoxine)
- a specialised low-protein diet
- medicine
With early diagnosis and treatment, most people with HCU live healthy lives. But they will need treatment for HCU for life.
Vitamin B6 (pyridoxine)
Vitamin B6 (pyridoxine) can help reduce the level of homocysteine in some babies. If this works, they will need to take vitamin B6 supplements for life.
Diet
A baby with HCU may not respond to vitamin B6. If they do not, they will be referred to a specialist metabolic dietitian. Your child will be on a low-protein diet to help keep their methionine levels low.
Your dietitian will give you detailed advice and guidance about feeding your baby. Your child will need some protein foods for healthy growth and development.
Your dietitian will ask you to check and measure your breast milk and infant formula. You may need to use a specialised HCU formula. This contains all the vitamins, minerals and other amino acids your baby needs.
Someone with HCU may need to follow a special diet for the rest of their life.
As your child gets older, they will need to:
- learn how to control their diet
- stay in contact with a dietitian for advice and monitoring
Medicine
Your child may be prescribed a medicine called betaine. This helps to clear some of the excess homocysteine.
Blood tests
Your child will need regular blood tests to check the amount of homocysteine in their blood.
How a child inherits HCU
HCU is caused by a faulty gene passed on by parents. The parents usually do not have any symptoms of the condition.
If you're a carrier of the faulty gene and you have a baby with someone who is also a carrier, your baby has a:
- 1 in 4 chance of developing HCU
- 1 in 2 chance of being a carrier of HCU
- 1 in 4 chance of receiving a pair of normal genes
