Homocystinuria

General Information for Families

 

Homocystinuria (HCY) is a hereditary error of metabolism. It is usually caused by a defective enzyme (cystathionine synthetase) needed to properly digest a component of food called methionine (an amino acid).

 

Inheritance and Frequency

Homocystinuria is thought to be inherited as an autosomal recessive genetic trait, which means the gene defect is unknowingly passed down from generation to generation. This faulty gene only emerges when two carriers have children together and pass it to their offspring. For each pregnancy of two such carriers, there is a 25% chance that the child will be born with the disease and a 50% chance the child will be a carrier for the gene defect.

Studies conducted since 1979 show that 1 of every 200,000 live births in the Unite States will have Homocystinuria. Prevalence in Great Britain, Ireland, and Australia is approximately 1 in 82,000 live births.

 

Signs & Symptoms

Symptoms associated with Homocystinuria may include mental retardation, seizures, psychiatric disturbances, delays in reaching developmental milestones (e.g., crawling, walking, sitting), displacement of the lens of the eye (ectopia lentis), abnormal thinning and weakness of the bones (osteoporosis and scoliosis ), and/or the formation of blood clots (thrombi) in various veins and arteries that may lead to life-threatening complications.

 

Long Term Effects
Optic lens dislocation may occur even with early treatment. Approximately 50% of untreated individuals die before age 25.

 

Treatment
It is treated initially by changing the baby to a formula that does not contain methionine. Treatment may also include a methionine-restricted and cystine-supplemented diet, as well as large doses of Vitamin B6.

 

Source: savebabies.org

 

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Family Questions & Concerns

 

What are amino acid disorders?
Amino acid disorders (AA disorders) cause the body to have problems breaking down certain proteins. The body breaks down, or metabolizes, food. The food is changed into nutrients they body can use, and the body gets rid of the chemicals it does not need. Enzymes(chemicals that do jobs in the body) usually help break down food. A person who has an AA disorder is missing a specific enzyme, or the enzyme is not working as well as it should. This prevents the body from breaking down protein in food, and toxic chemicals build up in the body. The build up of toxic chemicals can cause serious damage to organs. Each enzyme deficiency causes a different AA disorder. A special diet and medication can prevent most problems.

 

What causes AA disorders?
AA disorders are inherited when both parents pass an abnormal AA gene to their child. This means both parents are carriers of a particular AA disorder. Carriers do not experience any health problems related to the AA disorder. When two carriers of a particular AA disorder have children together, there is a 1 in 4 (25%) chance for each baby to have the AA disorder.

 

How are AA disorders detected?
Newborn screening is done on tiny samples of blood taken from the infant’s heel 24-48 hours after birth. After a positive newborn screen, testing at special labs must be done to know for sure if a baby has an AA disorder.

 

What problems can AA disorders cause?
An AA disorder is different for each child. Untreated AA disorders can cause vomiting, eye problems, liver problems, mental retardation, and possibly coma or death. It is extremely important to follow the doctor’s instructions about caring for a child with an AA disorder.

 

What is the treatment for AA disorders?
AA disorders can be treated. People with AA disorders should not eat certain proteins that the body has trouble breaking down. Medication may help the body get rid of harmful toxins. The treatment is life-long. For children who have an AA disorder:

  • The child should have a primary care doctor, a pediatric metabolic specialist, and a dietician. These health professionals give the child good medical care and educate the family about the special diet.
  • Families are taught to read labels carefully when shopping for food.
  • Treatment for an AA disorder is lifelong, and a child with an AA disorder should see a doctor regularly.

 

Source: Minnesota Newborn Screening Program

 

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National and State Specific Family Resources

 

 

View National and State Specific Family Resources

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Homocystinuria Prevalence by State

 

The Region 4 Newborn Screening Data, summarized annually, provides detailed data on newborn screening results within Illinois, Indiana, Kentucky, Michigan, Minnesota, Ohio and Wisconsin. It is provided here to: assist families and physicians in knowing the relative number of confirmed annual cases for the disorder within each state and how it compares to other states in the region. assist families and specialists across states in connecting with specialists who may have experience treating a specific rare disorder. It is important to note that ongoing developments in the sophistication of technology allows states to progressively increase the number of disorders they screen in their program.

 

2005 Confirmed Cases
State: IL IN OH MI WI MN KY TOTALS
Total Births: 175659 85570 144509 124942 70934 71058 52222 724894
Total Specimens: 182799 107983 151193 133680 74887 73857 0 724399
2005 0 0 0 0 0 0 0 0

2004 Confirmed Cases
State: IL IN OH MI WI MN KY TOTALS
Total Births: 177603 87942 142023 134103 66625 70579 50930 729805
Total Specimens: 183727 107852 151296 127572 68895 71791 53583 764716
2004 0 0 0 0 1 0 0 1

2003 Confirmed Cases
State: IL IN OH MI WI MN KY TOTALS
Total Births: 182590 86382 151983 130937 70053 70157 55281 747383
Total Specimens: 185033 109133 152211 128970 73362 71095 53381 773185
2003 1 0 0 0 0 0 0 1

2002 Confirmed Cases
State: IL IN OH MI WI MN KY TOTALS
Total Births: 180622 84618 148720 129967 68560 68025 54233 734745
Total Specimens: 184033 109360 152561 127978 71634 67839 52775 766180
2002 0 0 0 0 0 0 0 0

About this Data

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