MAPLE SYRUP URINE DISEASE
Maple syrup urine disease (MSUD) is a metabolism disorder passed down through families in which the body cannot break down certain parts of proteins. Urine in persons with this condition can smell like maple syrup.
CAUSES
- The four varieties of MSUD are caused by mutations, or changes, in the genes that tell your body to make certain enzymes. Gene mutations are inherited on the chromosomes you received from your parents. When the genes related to the BCKAD enzymes are defective, the BCKAD enzymes are not produced or work inaccurately.
- MSUD is a recessive genetic disorder. All forms of MSUD are received from your parents.
- Typically, parents of children with MSUD do not have the disease. They possess one mutated gene and one normal gene for MSUD. Though they carry the defective gene, they are not affected by it. The defective gene is called recessive. Parents of children with MSUD are called carriers.
- Having MSUD means that you inherited one flawed gene for MSUD from each parent. Both parents must carry a mutation of the gene associated with MSUD to pass the disease on to their child.
SYMPTOMS
Symptoms of MSUD vary according to the disease subtype. In classic MSUD, the most common type of the disease, symptoms become present in an infant within a few days after birth. The onset is usually triggered when the infant’s body begins to process protein from feedings.
Some of the initial symptoms characteristic of classic MSUD are:
Symptoms of MSUD vary according to the disease subtype. In classic MSUD, the most common type of the disease, symptoms become present in an infant within a few days after birth. The onset is usually triggered when the infant’s body begins to process protein from feedings.
Some of the initial symptoms characteristic of classic MSUD are:
- lethargy
- poor appetite
- weight loss
- weak sucking ability
- irritability
- a distinctive maple sugar odor in earwax, sweat, and urine
- irregular sleep patterns
- alternating episodes of hypertonia (muscle rigidity) and hypotonia (muscle limpness)
- high-pitched cry
- seizures
- neurological deficiencies
- developmental delays
- feeding problems
- poor growth
- a distinctive maple sugar odor in earwax, sweat, and urine
- lethargy
- a distinctive maple sugar odor in earwax, sweat, and urine
- ataxia (lack of voluntary coordination of muscle movement)
EXAMS AND TESTS
- Plasma amino acid test
- Urine amino acid test
TREATMENT
- Treatment involved dietary restriction of the amino acids leucine, isoleucine, and valine. This treatment must begin very early to prevent brain damage. Babies with the disease must eat a special formula that does not contain the amino acids leucine, isoleucine, and valine. As the person grows to adulthood, he or she must always watch their diet, avoiding high-protein foods such as meat, eggs, and nuts.
- If levels of the three amino acids still get too high, patients can be treated with an intravenous (given through a vein) solution that helps the body use up excess leucine, isoleucine, and valine for protein synthesis.
- Gene therapy is also a potential future treatment for patients with MSUD. This treatment would involve replacing the mutated gene with a good copy, allowing the patient's cells to make a functional BCKD protein complex and break down the excess amino acids.
POSSIBLE COMPLICATIONS
- Coma
- Death
- Neurological damage
PREVENTION
- Since MSUD is an inherited disease, there is no technique for prevention. A genetic counselor can help you determine your risk for having a baby with MSUD. Genetic testing can tell you if you or your partner is a carrier of the disease. DNA testing can identify the disease in a fetus before birth.
- Genetic counseling is suggested for people who want to have children and who have a family history of maple syrup urine disease. Many states now screen all newborns with blood tests for MSUD.
- If a screening test shows that your baby may have MSUD, a follow-up blood test for amino acid levels should be done right away to confirm the disease.