What is Homocystinuria (HCU)?
Homocystinuria (HCU), pronounced ho-mo-sis-tin-ur-ee-a, is a rare but treatable inherited disorder that prevents the normal breakdown of protein.
Babies with HCU inherit two faulty copies of the gene for HCU, one from each parent.
When we eat, our body breaks down protein in food into smaller parts called amino acids. Special chemicals found naturally in our body, called enzymes, then make changes to the amino acids so our body can use them.
If a baby has HCU, one of these amino acids (methionine) does not break down in the usual way. This means methionine and a chemical called homocysteine build up in the blood.
Babies with HCU benefit significantly from early treatment and can live healthy and active
lives. Without early diagnosis and treatment, HCU can lead to long term health problems including learning difficulties.
Symptoms of HCU
HCU may affect different babies in different ways. Babies with HCU are usually well in early life, although symptoms may develop later if untreated.
Some babies can develop problems with their eyes, including severe short sightedness and dislocation of the lens which may cause blurred vision. Without early treatment, babies can develop damage to the brain, including learning difficulties. Babies might also develop thin bones (osteoporosis), bone and joint problems and develop blood clots or strokes.
Treatment
In a few babies with HCU, the level of the chemical homocysteine can be controlled by giving vitamin B6 (pyridoxine). If this does not work, treatment for HCU involves a special low protein diet and medication.
The aim of the diet is to reduce the build-up of homocysteine which can cause learning difficulties and brain injury.
As high protein foods and milk (including breast milk and normal infant formula) have to be limited, a special infant formula which does not contain methionine is given to meet all nutritional requirements. This special infant formula is very important because it allows normal growth and development as well as helping to reduce the build-up of harmful toxins in the brain.
Your specialist metabolic dietitian will teach you how to measure and control the amount of protein you give to your baby, including breast milk feeds.
Your baby will need regular blood tests to monitor the levels of homocysteine in their blood.