Homocystinuria

• In Ontario, a heel prick is used to take a few drops of blood from each baby shortly after birth. The blood is tested for more than 25 treatable diseases, including homocystinuria.
• A screen positive result means that more tests are needed to know whether or not a baby has homocystinuria. It does not mean that a baby has homocystinuria. Babies identified at a young age through screening can be treated early to help prevent health problems.

Homocystinuria is a rare, inherited (genetic) disease.

• Babies with homocystinuria cannot break down methionine.
• Methionine is a building block of protein (also called an amino acid). It is found in many foods, including breast milk and infant formula.
• There are two types of homocystinuria. One that responds well to treatment with Vitamin B6, and one that does not respond.

• It is normal for parents and guardians to feel worried when their baby has a screen positive result. A ‘screen positive’ result does not mean that a baby has homocystinuria. It means that there is a chance that the baby may have homocystinuria.
• Follow-up testing is important to find out whether the baby truly has homocystinuria.
• The baby’s health care provider or a health care provider at a newborn screening treatment centre will discuss the results with the baby’s family.
• Follow-up testing is arranged as soon as possible and involves blood and urine tests.
• It can take a few days to weeks to find out if a baby truly has homocystinuria or not. This waiting period can be hard for families and it is natural for parents/guardians to feel worried when their baby has a screen positive result.

• Normal – the baby does not have homocystinuria.
• Abnormal – the baby does have homocystinuria and will need treatment. The family will be supported by a team of caring specialists.
• Inconclusive – more testing is required. The baby will continue to be followed closely by a specialist to ensure that he/she receives optimal care.

Most babies with homocystinuria appear normal at birth.

Early treatment helps to prevent serious and life-threatening health problems such as:

• developmental delay
• heart disease and stroke
• pancreatitis

• Treatment begins as early as possible after a diagnosis is made.
• Treatment involves medication, a special diet that is low in protein (low in methionine), medical formula, and supplements.
• Treatment is lifelong.
• A team, including a metabolic doctor and a dietitian, cares for babies with homocystinuria.
• Babies with homocystinuria have their health and development checked regularly.
• Regular follow-up tests are used to monitor and adjust treatments.

• Children with homocystinuria can be as healthy and intelligent as other children their age if methionine levels are well managed with diet and medication.
• Even with treatment, some children may develop eye problems.